diff --git a/.stylelintrc b/.stylelintrc
index a58e7ab8da..fc50e40c1c 100644
--- a/.stylelintrc
+++ b/.stylelintrc
@@ -62,7 +62,7 @@
 		"declaration-empty-line-before": "never",
 
 		"declaration-property-unit-blacklist": {
-			"line-height": ["rem", "px", "em", "%"]
+			"line-height": ["rem", "em", "%"]
 		},
 		"declaration-property-unit-whitelist": {
 			"height": ["px", "%", "vh"],
diff --git a/phpBB/styles/prosilver/theme/base.css b/phpBB/styles/prosilver/theme/base.css
index 3c5fdb11d5..f4daeee1e5 100644
--- a/phpBB/styles/prosilver/theme/base.css
+++ b/phpBB/styles/prosilver/theme/base.css
@@ -15,15 +15,15 @@
 }
 */
 
-/* Define your base font-size here; most elements will inherit this. */
-
+/*
+ * 1. Define your base font-size here (16px), most elements will inherit this.
+ * 2. 24px (This is now our magic number; all subsequent margin-bottoms and
+ *    line-heights want to be a multiple of this number in order to maintain
+ *    vertical rhythm.)
+*/
 html {
-	font-size: 16px; /* Assuming 16px... */
-
-	/* 24px (This is now our magic number; all subsequent margin-bottoms and
-	line-heights want to be a multiple of this number in order to maintain
-	vertical rhythm.) */
-	line-height: 1.5;
+	font-size: 16px; /* [1] */
+	line-height: 1.5; /* [2] */
 	-webkit-tap-highlight-color: rgba(0, 0, 0, 0);
 }
 
diff --git a/phpBB/styles/prosilver/theme/bidi.css b/phpBB/styles/prosilver/theme/bidi.css
index 41520f0164..40309aa642 100644
--- a/phpBB/styles/prosilver/theme/bidi.css
+++ b/phpBB/styles/prosilver/theme/bidi.css
@@ -3,7 +3,6 @@
 /* -------------------------------------------------------------- */
 /* stylelint-disable selector-max-compound-selectors */
 /* stylelint-disable selector-no-qualifying-type */
-/* stylelint-disable declaration-property-unit-whitelist */
 
 /**
 * common.css
@@ -196,8 +195,9 @@
 	text-align: right;
 }
 
+/* Not used anywhere maybe deprecated? */
 .rtl table.table1 thead .autocol {
-	padding-right: 1em;
+	padding-right: 10px;
 	padding-left: 0;
 }
 
@@ -295,6 +295,11 @@
 	margin-left: 5px;
 }
 
+.rtl .topic-poster {
+	float: right;
+	padding-left: 6px;
+}
+
 /* Action Bar styles
 ---------------------------------------- */
 .rtl .action-bar .button {
@@ -513,7 +518,7 @@ li.breadcrumbs span:first-child > a {
 ---------------------------------------- */
 .rtl .content ul,
 .rtl .content ol {
-	margin-right: 3em;
+	margin-right: 40px;
 	margin-left: 0;
 }
 
@@ -535,12 +540,12 @@ li.breadcrumbs span:first-child > a {
 
 /* Quote block */
 .rtl blockquote {
-	margin: 0.5em 25px 0 1px;
+	margin: 5px 25px 0 1px;
 }
 
 /* Nested quotes */
 .rtl blockquote blockquote {
-	margin: 0.5em 15px 0 1px;
+	margin: 5px 15px 0 1px;
 }
 
 /* Username/source of quoter */
@@ -697,7 +702,7 @@ li.breadcrumbs span:first-child > a {
 }
 
 .rtl .cp-main .panel ol {
-	margin-right: 2em;
+	margin-right: 22px;
 	margin-left: 0;
 }
 
@@ -820,7 +825,7 @@ li.breadcrumbs span:first-child > a {
 
 .rtl option {
 	padding-right: 0;
-	padding-left: 1em;
+	padding-left: 11px;
 }
 
 .rtl label {
@@ -849,7 +854,7 @@ li.breadcrumbs span:first-child > a {
 .rtl fieldset.fields1 dd {
 	border-right-width: 0;
 	border-left-width: 1px;
-	margin-right: 15em;
+	margin-right: 165px;
 	margin-left: 0;
 }
 
@@ -862,7 +867,7 @@ li.breadcrumbs span:first-child > a {
 .rtl fieldset.fields2 dd {
 	border-right-width: 0;
 	border-left-width: 1px;
-	margin-right: 16em;
+	margin-right: 176px;
 	margin-left: 0;
 }
 
@@ -902,7 +907,7 @@ li.breadcrumbs span:first-child > a {
 .rtl fieldset.display-actions {
 	text-align: left;
 	padding-right: 0;
-	padding-left: 1em;
+	padding-left: 11px;
 }
 
 .rtl fieldset.display-actions label {
@@ -985,4 +990,3 @@ li.breadcrumbs span:first-child > a {
 }
 
 /* stylelint-enable selector-no-qualifying-type */
-/* stylelint-enable declaration-property-unit-whitelist */
diff --git a/phpBB/styles/prosilver/theme/buttons.css b/phpBB/styles/prosilver/theme/buttons.css
index 7d98aeda65..3bbcc51ef5 100644
--- a/phpBB/styles/prosilver/theme/buttons.css
+++ b/phpBB/styles/prosilver/theme/buttons.css
@@ -2,8 +2,6 @@
 	$Buttons
 /* -------------------------------------------------------------- */
 
-/* stylelint-disable declaration-property-unit-whitelist */
-
 .button {
 	font-family: "Open Sans", "Droid Sans", Verdana, Arial, Helvetica;
 	font-size: 13px;
@@ -156,7 +154,7 @@
 }
 
 .post-buttons .dropdown a {
-	font-size: 1.2em;
+	font-size: 13px;
 	text-align: right;
 	display: block;
 }
@@ -207,5 +205,3 @@ ul.linklist.bulletin > li.small-icon:before {
 	padding-right: 19px;
 	padding-left: 0;
 }
-
-/* stylelint-enable declaration-property-unit-whitelist */
diff --git a/phpBB/styles/prosilver/theme/common.css b/phpBB/styles/prosilver/theme/common.css
index b23ba358d2..36b7809bbc 100644
--- a/phpBB/styles/prosilver/theme/common.css
+++ b/phpBB/styles/prosilver/theme/common.css
@@ -3,8 +3,6 @@
 /* -------------------------------------------------------------- */
 /* stylelint-disable selector-max-compound-selectors */
 /* stylelint-disable selector-no-qualifying-type */
-/* stylelint-disable declaration-property-unit-whitelist */
-/* stylelint-disable declaration-property-unit-blacklist */
 
 html {
 	font-size: 100%;
@@ -15,7 +13,7 @@ html {
 
 body {
 	font-family: Verdana, Helvetica, Arial, sans-serif;
-	font-size: 10px;
+	font-size: 16px;
 	line-height: normal;
 	word-wrap: break-word;
 	margin: 0;
@@ -26,7 +24,7 @@ body {
 h1 {
 	/* Forum name */
 	font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;
-	font-size: 2em;
+	font-size: 20px;
 	font-weight: bold;
 	margin-top: 15px;
 	margin-right: 200px;
@@ -35,19 +33,19 @@ h1 {
 h2 {
 	/* Forum header titles */
 	font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;
-	font-size: 2em;
+	font-size: 20px;
 	font-weight: normal;
 	margin: 0.8em 0 0.2em;
 }
 
 h2.solo {
-	margin-bottom: 1em;
+	margin-bottom: 20px;
 }
 
 h3 {
 	/* Sub-headers (also used as post headers, but defined later) */
 	font-family: Arial, Helvetica, sans-serif;
-	font-size: 1.05em;
+	font-size: 12px;
 	font-weight: bold;
 	text-transform: uppercase;
 	border-bottom: 1px solid transparent;
@@ -59,13 +57,13 @@ h3 {
 h4 {
 	/* Forum and topic list titles */
 	font-family: "Trebuchet MS", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1.3em;
+	font-size: 13px;
 }
 
 p {
-	font-size: 1.1em;
-	line-height: 1.3em;
-	margin-bottom: 1.5em;
+	font-size: 11px;
+	line-height: 14px;
+	margin-bottom: 16px;
 }
 
 img {
@@ -263,8 +261,8 @@ ul.linklist {
 }
 
 ul.linklist > li {
-	font-size: 1.1em;
-	line-height: 2.2em;
+	font-size: 11px;
+	line-height: 24px;
 	float: left;
 	width: auto;
 	margin-right: 7px;
@@ -543,7 +541,7 @@ a.header-avatar span:after {
 }
 
 .dropdown li {
-	font-size: 1em !important;
+	font-size: 11px !important;
 	line-height: normal !important;
 	text-align: left;
 	white-space: nowrap;
@@ -623,15 +621,15 @@ a.header-avatar span:after {
 }
 
 .breadcrumbs.wrapped .crumb a {
-	letter-spacing: -0.3px;
+	letter-spacing: -0.019em;
 }
 
 .breadcrumbs.wrapped .crumb.wrapped-medium a {
-	letter-spacing: -0.4px;
+	letter-spacing: -0.025em;
 }
 
 .breadcrumbs.wrapped .crumb.wrapped-tiny a {
-	letter-spacing: -0.5px;
+	letter-spacing: -0.031em;
 }
 
 .breadcrumbs .crumb.wrapped-max a {
@@ -665,9 +663,9 @@ table.table1 {
 }
 
 table.table1 thead th {
-	font-size: 1em;
+	font-size: 10px;
 	font-weight: normal;
-	line-height: 1.3em;
+	line-height: 13px;
 	text-transform: uppercase;
 	padding: 0 0 4px 3px;
 }
@@ -681,7 +679,7 @@ table.table1 tbody tr {
 }
 
 table.table1 td {
-	font-size: 1.1em;
+	font-size: 11px;
 }
 
 table.table1 tbody td {
@@ -740,12 +738,12 @@ table.table1 .info div {
 }
 
 table.table1 .autocol {
-	line-height: 2em;
+	line-height: 22px;
 	white-space: nowrap;
 }
 
 table.table1 thead .autocol {
-	padding-left: 1em;
+	padding-left: 10px;
 }
 
 table.table1 span.rank-img {
@@ -813,8 +811,8 @@ table.info tbody th {
 }
 
 dl.details {
-	/* font-family: "Lucida Grande", Verdana, Helvetica, Arial, sans-serif; */
-	font-size: 1.1em;
+	font-family: "Lucida Grande", Verdana, Helvetica, Arial, sans-serif;
+	font-size: 11px;
 }
 
 dl.details dt {
@@ -851,7 +849,13 @@ fieldset.fields1 ul.recipients {
 
 fieldset.fields1 dd.recipients {
 	clear: left;
-	margin-left: 1em;
+	margin-left: 11px;
+}
+
+fieldset.fields1 ul.recipients input.button2 {
+	font-size: 12px;
+	margin-right: 0;
+	padding: 0;
 }
 
 fieldset.fields1 dl.pmlist > dt {
@@ -870,7 +874,7 @@ fieldset.fields1 dl.pmlist dd.recipients {
 }
 
 .forabg + .action-bar {
-	margin-top: 2em;
+	margin-top: 12px;
 }
 
 .action-bar .button {
@@ -946,6 +950,7 @@ fieldset.fields1 dl.pmlist dd.recipients {
 
 .pagination li.page-jump a i {
 	font-size: 21px;
+	line-height: 21px;
 }
 
 .pagination .arrow a {
@@ -1007,7 +1012,7 @@ fieldset.fields1 dl.pmlist dd.recipients {
 .phpbb_alert div.alert_text > select,
 .phpbb_alert div.alert_text > textarea,
 .phpbb_alert div.alert_text > input {
-	font-size: 1.1em;
+	font-size: 11px;
 }
 
 .darkenwrapper {
@@ -1083,12 +1088,13 @@ fieldset.fields1 dl.pmlist dd.recipients {
 /* Miscellaneous styles
 ---------------------------------------- */
 .copyright {
+	font-size: 10px;
 	text-align: center;
 	padding: 5px;
 }
 
 .small {
-	font-size: 0.9em !important;
+	font-size: 90% !important;
 }
 
 .titlespace {
@@ -1100,12 +1106,12 @@ fieldset.fields1 dl.pmlist dd.recipients {
 }
 
 .error {
-	font-size: 1em;
+	font-size: 10px;
 	font-weight: bold;
 }
 
 div.rules {
-	font-size: 1.1em;
+	font-size: 11px;
 	border-radius: 7px;
 	margin: 10px 0;
 	padding: 5px 10px;
@@ -1119,7 +1125,7 @@ div.rules ol {
 p.post-notice {
 	position: relative;
 	min-height: 14px;
-	margin-bottom: 1em;
+	margin-bottom: 11px;
 	padding: 5px;
 }
 
@@ -1159,12 +1165,14 @@ ul.linklist:after,
 	content: "";
 }
 
+/* stylelint-disable declaration-property-unit-whitelist */
 .emoji {
 	width: 1em;
 	min-width: 18px;
 	height: 1em;
 	min-height: 18px;
 }
+/* stylelint-enable declaration-property-unit-whitelist */
 
 .smilies {
 	vertical-align: text-bottom;
@@ -1181,7 +1189,7 @@ ul.linklist:after,
 }
 
 .member-search strong {
-	font-size: 0.95em;
+	font-size: 11px;
 }
 
 .dropdown-extended {
@@ -1197,7 +1205,6 @@ ul.linklist:after,
 }
 
 .dropdown-extended .dropdown-extended-item {
-	font-size: 0.95em;
 	border-top: 1px solid;
 	position: relative;
 	float: none;
@@ -1229,11 +1236,13 @@ ul.linklist:after,
 .dropdown-extended .header {
 	font-family: Arial, "Helvetica Neue", Helvetica, Arial, sans-serif;
 	font-weight: bold;
-	line-height: 3em;
+	line-height: 33px;
 	text-align: left;
 	text-transform: uppercase;
 	border-bottom: 1px solid;
 	border-radius: 5px 5px 0 0;
+
+	/* needs moved to colurs.css */
 	text-shadow: 1px 1px 1px #ffffff;
 	padding: 0 10px;
 }
@@ -1256,7 +1265,7 @@ ul.linklist:after,
 }
 
 .dropdown-extended .footer {
-	font-size: 1.1em;
+	font-size: 12px;
 	text-align: center;
 }
 
@@ -1288,7 +1297,6 @@ ul.linklist:after,
 }
 
 .notification-item p {
-	font-size: 1em;
 	margin-bottom: 4px;
 }
 
@@ -1301,7 +1309,7 @@ ul.linklist:after,
 }
 
 .notification-time {
-	font-size: 0.9em;
+	font-size: 10px;
 	text-align: right;
 	margin: 0;
 }
@@ -1317,7 +1325,7 @@ ul.linklist:after,
 
 .notifications-title {
 	font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;
-	font-size: 1.2em !important;
+	font-size: 13px !important;
 }
 
 .notifications-title strong {
@@ -1325,7 +1333,7 @@ ul.linklist:after,
 }
 
 .notifications-time {
-	font-size: 0.9em !important;
+	font-size: 10px !important;
 }
 
 .notification-text {
@@ -1382,5 +1390,5 @@ ul.linklist:after,
 	border-top: none;
 }
 
-/* stylelint-enable declaration-property-unit-whitelist */
-/* stylelint-enable declaration-property-unit-blacklist */
+/* stylelint-enable selector-max-compound-selectors */
+/* stylelint-enable selector-no-qualifying-type */
diff --git a/phpBB/styles/prosilver/theme/content.css b/phpBB/styles/prosilver/theme/content.css
index b35763841a..8e1ccc0b31 100644
--- a/phpBB/styles/prosilver/theme/content.css
+++ b/phpBB/styles/prosilver/theme/content.css
@@ -4,8 +4,6 @@
 
 /* stylelint-disable selector-max-compound-selectors */
 /* stylelint-disable selector-no-qualifying-type */
-/* stylelint-disable declaration-property-unit-whitelist */
-/* stylelint-disable declaration-property-unit-blacklist */
 
 ul.topiclist {
 	display: block;
@@ -34,7 +32,7 @@ ul.topiclist dd {
 }
 
 ul.topiclist dt {
-	font-size: 1.1em;
+	font-size: 11px;
 	width: 100%;
 	margin-right: -440px;
 }
@@ -112,8 +110,8 @@ li.row strong {
 li.header dt,
 li.header dd {
 	font-family: Arial, Helvetica, sans-serif;
-	font-size: 1em;
-	line-height: 1em;
+	font-size: 10px;
+	line-height: 10px;
 	text-transform: uppercase;
 	border-left-width: 0;
 	margin: 2px 0 4px;
@@ -176,7 +174,8 @@ dl.row-item dt a {
 	display: inline;
 }
 
-dl a.row-item-link {						/* topic row icon links */
+/* topic row icon links */
+dl a.row-item-link {
 	position: absolute;
 	top: 50%;
 	left: 0;
@@ -193,8 +192,8 @@ dd.topics,
 dd.views,
 dd.extra,
 dd.mark {
-	font-size: 1.2em;
-	line-height: 2.2em;
+	font-size: 12px;
+	line-height: 26px;
 	text-align: center;
 	width: 80px;
 }
@@ -208,7 +207,7 @@ dd.views {
 /* List in forum description */
 dl.row-item dt ol,
 dl.row-item dt ul {
-	margin-left: 1em;
+	margin-left: 10px;
 	list-style-position: inside;
 }
 
@@ -222,16 +221,16 @@ dd.redirect,
 dd.moderation,
 dd.time,
 dd.info {
-	font-size: 1.1em;
+	font-size: 11px;
 	width: 250px;
 }
 
 dd.redirect {
-	line-height: 2.5em;
+	line-height: 26px;
 }
 
 dd.time {
-	line-height: 200%;
+	line-height: 22px;
 }
 
 dd.lastpost > span,
@@ -245,12 +244,12 @@ dd.moderation > span {
 
 dd.extra,
 dd.mark {
-	line-height: 200%;
+	line-height: 24px;
 }
 
 dd.option {
-	font-size: 1.1em;
-	line-height: 200%;
+	font-size: 11px;
+	line-height: 22px;
 	text-align: center;
 	width: 125px;
 }
@@ -258,7 +257,7 @@ dd.option {
 /* Post body styles
 ---------------------------------------- */
 .postbody {
-	line-height: 1.48em;
+	line-height: 16px;
 	position: relative;
 	float: left;
 	width: 76%;
@@ -266,25 +265,25 @@ dd.option {
 }
 
 .postbody .ignore {
-	font-size: 1.1em;
+	font-size: 11px;
 }
 
 .postbody h3.first {
 	/* The first post on the page uses this */
-	font-size: 1.7em;
+	font-size: 17px;
 }
 
 .postbody h3 {
 	font-family: "Trebuchet MS", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1.5em;
-	line-height: 125%;
+	font-size: 15px;
+	line-height: 19px;
 	text-transform: none;
 	border: none;
 
 	/* Postbody requires a different h3 format - so change it here */
 	float: left;
 	margin-top: 0 !important;
-	margin-bottom: 0.3em !important;
+	margin-bottom: 4px !important;
 	padding: 2px 0 0;
 }
 
@@ -299,7 +298,7 @@ dd.option {
 }
 
 .postbody .content {
-	font-size: 1.3em;
+	font-size: 13px;
 	overflow-x: auto;
 }
 
@@ -315,7 +314,7 @@ dd.option {
 /* Topic review panel
 ---------------------------------------- */
 .panel .review {
-	margin-top: 2em;
+	margin-top: 20px;
 }
 
 .topicreview {
@@ -355,22 +354,22 @@ dd.option {
 ---------------------------------------- */
 .content {
 	font-family: "Lucida Grande", "Trebuchet MS", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1em;
-	line-height: 1.4em;
+	font-size: 10px;
+	line-height: 14px;
 	clear: both;
 	overflow: hidden;
-	min-height: 3em;
+	min-height: 30px;
 	padding-bottom: 1px;
 }
 
 .content h2,
 .panel h2 {
-	font-size: 1.6em;
+	font-size: 16px;
 	font-weight: normal;
 	border-bottom: 1px solid transparent;
-	margin-top: 0.5em;
-	margin-bottom: 0.5em;
-	padding-bottom: 0.5em;
+	margin-top: 8px;
+	margin-bottom: 8px;
+	padding-bottom: 8px;
 }
 
 .panel h3 {
@@ -378,24 +377,21 @@ dd.option {
 }
 
 .panel p {
-	font-size: 1.2em;
-	line-height: 1.4em;
-	margin-bottom: 1em;
+	font-size: 12px;
+	line-height: 16px;
+	margin-bottom: 12px;
 }
 
 .content p {
 	font-family: "Lucida Grande", "Trebuchet MS", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1.2em;
-	line-height: 1.4em;
-	margin-bottom: 1em;
 }
 
 dl.faq {
 	font-family: "Lucida Grande", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1.1em;
-	line-height: 1.4em;
-	margin-top: 1em;
-	margin-bottom: 2em;
+	font-size: 11px;
+	line-height: 15px;
+	margin-top: 11px;
+	margin-bottom: 22px;
 }
 
 dl.faq dt {
@@ -403,8 +399,8 @@ dl.faq dt {
 }
 
 .content dl.faq {
-	font-size: 1.2em;
-	margin-bottom: 0.5em;
+	font-size: 12px;
+	margin-bottom: 6px;
 }
 
 .content li {
@@ -423,23 +419,23 @@ dl.faq dt {
 /* Post author */
 p.author {
 	font-family: Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1em;
-	line-height: 1.2em;
+	font-size: 10px;
+	line-height: 12px;
 	clear: both;
-	margin-bottom: 0.6em;
+	margin-bottom: 8px;
 	padding: 0 0 5px;
 }
 
 /* Post signature */
 .signature {
-	font-size: 1.1em;
-	line-height: 140%;
+	font-size: 11px;
+	line-height: 16px;
 	border-top: 1px solid transparent;
 	clear: left;
 	overflow: hidden;
 	width: 100%;
-	margin-top: 1.5em;
-	padding-top: 0.2em;
+	margin-top: 16px;
+	padding-top: 2px;
 }
 
 .signature.standalone {
@@ -460,19 +456,19 @@ dd .signature {
 
 .signature ul,
 .signature ol {
-	margin: 0.8em 0 0.9em 3em;
+	margin: 10px 0 10px 33px;
 }
 
 /* Post noticies */
 .notice {
 	font-family: "Lucida Grande", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1em;
-	line-height: 130%;
+	font-size: 10px;
+	line-height: 13px;
 	border-top: 1px dashed transparent;
 	clear: left;
 	width: auto;
-	margin-top: 1.5em;
-	padding-top: 0.2em;
+	margin-top: 15px;
+	padding-top: 2px;
 }
 
 /* Jump to post link for now */
@@ -487,21 +483,21 @@ ul.searchresults {
 
 /* Quote block */
 blockquote {
-	font-size: 0.95em;
+	font-size: 10px;
 	border: 1px solid transparent;
 	overflow: hidden;
-	margin: 1em 1px 1em 25px;
+	margin: 10px 1px 10px 25px;
 	padding: 5px;
 }
 
 blockquote blockquote {
 	/* Nested quotes */
-	font-size: 1em;
-	margin: 1em 1px 1em 15px;
+	font-size: 10px;
+	margin: 10px 1px 10px 15px;
 }
 
 blockquote cite {
-	font-size: 0.9em;
+	font-size: 9px;
 	font-weight: bold;
 
 	/* Username/source of quoter */
@@ -510,7 +506,7 @@ blockquote cite {
 }
 
 blockquote cite cite {
-	font-size: 1em;
+	font-size: 10px;
 }
 
 blockquote cite:before,
@@ -530,14 +526,14 @@ blockquote cite > div {
 
 /* Code block */
 .codebox {
-	font-size: 1em;
+	font-size: 13px;
 	word-wrap: normal;
 	border: 1px solid transparent;
-	margin: 1em 0 1.2em;
+	margin: 13px 0 16px;
 }
 
 .codebox p {
-	font-size: 0.8em !important;
+	font-size: 10px !important;
 	font-weight: bold;
 	text-transform: uppercase;
 	border-bottom: 1px solid transparent;
@@ -551,8 +547,8 @@ blockquote .codebox {
 }
 
 .codebox code {
-	font: 0.9em Monaco, "Andale Mono", "Courier New", Courier, monospace;
-	line-height: 1.3em;
+	font: 12px Monaco, "Andale Mono", "Courier New", Courier, monospace;
+	line-height: 15px;
 	display: block;
 	overflow: auto;
 	height: auto;
@@ -592,13 +588,13 @@ blockquote .codebox {
 
 .attachbox p {
 	font-weight: normal;
-	line-height: 110%;
+	line-height: 12px;
 	clear: left;
 }
 
 .attachbox p.stats {
 	font-weight: normal;
-	line-height: 110%;
+	line-height: 12px;
 	clear: left;
 }
 
@@ -669,7 +665,7 @@ fieldset.polls {
 }
 
 fieldset.polls dl {
-	line-height: 120%;
+	line-height: 13px;
 	border-top: 1px solid transparent;
 	margin-top: 5px;
 	padding: 5px 0 0;
@@ -680,7 +676,7 @@ fieldset.polls dl.voted {
 }
 
 fieldset.polls dt {
-	font-size: 1.1em;
+	font-size: 11px;
 	text-align: left;
 	border-right: none;
 	display: block;
@@ -691,7 +687,7 @@ fieldset.polls dt {
 }
 
 fieldset.polls dd {
-	font-size: 1.1em;
+	font-size: 11px;
 	border-left: none;
 	float: left;
 	width: 10%;
@@ -726,7 +722,7 @@ fieldset.polls dd div {
 }
 
 .vote-submitted {
-	font-size: 1.2em;
+	font-size: 12px;
 	font-weight: bold;
 	text-align: center;
 }
@@ -745,7 +741,8 @@ fieldset.polls dd div {
 
 .postprofile dd,
 .postprofile dt {
-	line-height: 1.2em;
+	font-size: 10px;
+	line-height: 12px;
 	margin-left: 8px;
 }
 
@@ -903,5 +900,3 @@ table.fixed-width-table {
 
 /* stylelint-enable selector-max-compound-selectors */
 /* stylelint-enable selector-no-qualifying-type */
-/* stylelint-enable declaration-property-unit-whitelist */
-/* stylelint-enable declaration-property-unit-blacklist */
diff --git a/phpBB/styles/prosilver/theme/cp.css b/phpBB/styles/prosilver/theme/cp.css
index 6d197df9c0..11ca6dd10c 100644
--- a/phpBB/styles/prosilver/theme/cp.css
+++ b/phpBB/styles/prosilver/theme/cp.css
@@ -4,15 +4,13 @@
 
 /* stylelint-disable selector-max-compound-selectors */
 /* stylelint-disable selector-no-qualifying-type */
-/* stylelint-disable declaration-property-unit-whitelist */
-/* stylelint-disable declaration-property-unit-blacklist */
 
 /* Main CP box
 ---------------------------------------- */
 .cp-menu {
 	float: left;
 	width: 19%;
-	margin-top: 1em;
+	margin-top: 10px;
 	margin-bottom: 5px;
 }
 
@@ -26,12 +24,12 @@
 }
 
 .panel-container .panel p {
-	font-size: 1.1em;
+	font-size: 11px;
 }
 
 .panel-container .panel ol {
-	font-size: 1.1em;
-	margin-left: 2em;
+	font-size: 11px;
+	margin-left: 22px;
 }
 
 .panel-container .panel li.row {
@@ -50,7 +48,7 @@ ul.cplist {
 }
 
 .panel-container table.table1 {
-	margin-bottom: 1em;
+	margin-bottom: 10px;
 }
 
 .panel-container table.table1 thead th {
@@ -82,7 +80,7 @@ ul.cplist {
 }
 
 .panel-container .postbody p.author {
-	font-size: 1.1em;
+	font-size: 11px;
 }
 
 .cp-main .buttons {
@@ -120,9 +118,9 @@ ul.cplist {
 
 .tabs .tab,
 .minitabs .tab {
-	font-size: 1em;
+	font-size: 10px;
 	font-weight: bold;
-	line-height: 1.4em;
+	line-height: 14px;
 	display: block;
 	float: left;
 }
@@ -182,8 +180,8 @@ ul.cplist {
 }
 
 .responsive-tab > a.responsive-tab-link {
-	font-size: 1.6em;
-	line-height: 0.9em;
+	font-size: 16px;
+	line-height: 14px;
 	text-decoration: none;
 	position: relative;
 	display: block;
@@ -191,19 +189,19 @@ ul.cplist {
 }
 
 .responsive-tab .responsive-tab-link:before {
-	border-top: 0.375em double transparent;
-	border-bottom: 0.125em solid transparent;
+	border-top: 6px double rgba(0, 0, 0, 0);
+	border-bottom: 2px solid rgba(0, 0, 0, 0);
 	position: absolute;
 	top: 7px;
 	left: 10px;
 	width: 14px;
-	height: 0.125em;
+	height: 2px;
 	content: "";
 }
 
 .tabs .dropdown,
 .minitabs .dropdown {
-	font-size: 1.1em;
+	font-size: 11px;
 	font-weight: normal;
 	top: 20px;
 	margin-right: -2px;
@@ -250,6 +248,7 @@ ul.cplist {
 
 /* Link styles for the sub-section links */
 .navigation a {
+	font-size: 10px;
 	text-decoration: none;
 	display: block;
 	margin: 1px 0;
@@ -270,6 +269,7 @@ ul.cplist {
 
 /* Friends list */
 .cp-mini {
+	font-size: 10px;
 	border-radius: 7px;
 	overflow-y: auto;
 	max-height: 200px;
@@ -302,7 +302,7 @@ ol.def-rules {
 }
 
 ol.def-rules li {
-	line-height: 180%;
+	line-height: 18px;
 	padding: 1px;
 }
 
@@ -353,7 +353,9 @@ ol.def-rules li {
 	padding: 5px;
 }
 
+.cplist .topictitle {
+	line-height: 30px;
+}
+
 /* stylelint-enable selector-max-compound-selectors */
 /* stylelint-enable selector-no-qualifying-type */
-/* stylelint-enable declaration-property-unit-whitelist */
-/* stylelint-enable declaration-property-unit-blacklist */
diff --git a/phpBB/styles/prosilver/theme/forms.css b/phpBB/styles/prosilver/theme/forms.css
index 853a88a129..6598f7955c 100644
--- a/phpBB/styles/prosilver/theme/forms.css
+++ b/phpBB/styles/prosilver/theme/forms.css
@@ -4,20 +4,18 @@
 
 /* stylelint-disable selector-max-compound-selectors */
 /* stylelint-disable selector-no-qualifying-type */
-/* stylelint-disable declaration-property-unit-whitelist */
-/* stylelint-disable declaration-property-unit-blacklist */
 
 /* General form styles
 ---------------------------------------- */
 fieldset {
 	font-family: Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1.1em;
+	font-size: 11px;
 	border-width: 0;
 }
 
 input {
 	font-family: Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1em;
+	font-size: 11px;
 	font-weight: normal;
 	vertical-align: middle;
 	padding: 0 3px;
@@ -25,7 +23,7 @@ input {
 
 select {
 	font-family: Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1em;
+	font-size: 11px;
 	font-weight: normal;
 	vertical-align: middle;
 	border: 1px solid transparent;
@@ -38,18 +36,18 @@ select:focus {
 }
 
 option {
-	padding-right: 1em;
+	padding-right: 11px;
 }
 
 select optgroup option {
 	font-family: Verdana, Helvetica, Arial, sans-serif;
-	padding-right: 1em;
+	padding-right: 11px;
 }
 
 textarea {
 	font-family: "Lucida Grande", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1em;
-	line-height: 1.4em;
+	font-size: 11px;
+	line-height: 18px;
 	width: 60%;
 	padding: 2px;
 }
@@ -86,16 +84,6 @@ fieldset dd {
 	margin-left: 41%;
 }
 
-/* Specific layout 1 */
-fieldset.fields1 dt {
-	border-right-width: 0;
-	width: 15em;
-}
-
-fieldset.fields1 dd {
-	border-left-width: 0;
-	margin-left: 15em;
-}
 
 fieldset.fields1 div {
 	margin-bottom: 3px;
@@ -106,15 +94,21 @@ fieldset.fields1 .live-search div {
 	margin-bottom: 0;
 }
 
-/* Specific layout 2 */
-fieldset.fields2 dt {
+/* Specific layouts */
+fieldset.fields2 dt,
+fieldset.fields1 dt {
 	border-right-width: 0;
-	width: 15em;
+	width: 165px;
 }
 
 fieldset.fields2 dd {
 	border-left-width: 0;
-	margin-left: 16em;
+	margin-left: 176px;
+}
+
+fieldset.fields1 dd {
+	border-left-width: 0;
+	margin-left: 165px;
 }
 
 /* Form elements */
@@ -191,7 +185,7 @@ fieldset.display-options a {
 }
 
 .dropdown fieldset.display-options {
-	font-size: 1em;
+	font-size: 11px;
 	margin: 0;
 	padding: 0;
 }
@@ -210,10 +204,10 @@ fieldset.display-options a {
 
 /* Display actions for ucp and mcp pages */
 fieldset.display-actions {
-	line-height: 2em;
+	line-height: 22px;
 	text-align: right;
 	white-space: nowrap;
-	padding-right: 1em;
+	padding-right: 11px;
 }
 
 fieldset.display-actions label {
@@ -221,8 +215,9 @@ fieldset.display-actions label {
 	padding-right: 2px;
 }
 
+/* Not used anywhere */
 fieldset.sort-options {
-	line-height: 2em;
+	line-height: 22px;
 }
 
 /* MCP forum selection */
@@ -267,7 +262,7 @@ fieldset.submit-buttons input {
 
 .message-box textarea {
 	font-family: "Trebuchet MS", Verdana, Helvetica, Arial, sans-serif;
-	font-size: 1.2em;
+	font-size: 13px;
 	outline: 3px dashed transparent;
 	outline-offset: -4px;
 	width: 450px;
@@ -414,5 +409,3 @@ input.search {
 
 /* stylelint-enable selector-max-compound-selectors */
 /* stylelint-enable selector-no-qualifying-type */
-/* stylelint-enable declaration-property-unit-whitelist */
-/* stylelint-enable declaration-property-unit-blacklist */
diff --git a/phpBB/styles/prosilver/theme/icons.css b/phpBB/styles/prosilver/theme/icons.css
index 18447171f0..5c453b1b6a 100644
--- a/phpBB/styles/prosilver/theme/icons.css
+++ b/phpBB/styles/prosilver/theme/icons.css
@@ -18,11 +18,11 @@ blockquote cite:before,
 	font-weight: normal;
 	font-style: normal;
 	font-variant: normal;
-	-webkit-font-smoothing: antialiased;
 	line-height: 1;
 	display: inline-block;
 	/* stylelint-disable order/declaration-block-properties-specified-order */
 	-moz-osx-font-smoothing: grayscale;
+	-webkit-font-smoothing: antialiased;
 	/* stylelint-enable order/declaration-block-properties-specified-order */
 	text-rendering: auto; /* optimizelegibility throws things off #1094 */
 }
@@ -86,7 +86,6 @@ blockquote cite:before,
 }
 
 .alert_close .icon:before {
-	line-height: 0.9;
 	border-radius: 50%;
 	display: block;
 	width: 11px;
diff --git a/phpBB/styles/prosilver/theme/links.css b/phpBB/styles/prosilver/theme/links.css
index 10bdd9e729..b83f49b0a2 100644
--- a/phpBB/styles/prosilver/theme/links.css
+++ b/phpBB/styles/prosilver/theme/links.css
@@ -2,8 +2,6 @@
 	$Links
 /* -------------------------------------------------------------- */
 
-/* stylelint-disable declaration-property-unit-whitelist */
-
 /* Links adjustment to correctly display an order of rtl/ltr mixed content */
 a {
 	text-decoration: none;
@@ -66,9 +64,10 @@ th a:hover {
 
 
 /* Links for forum/topic lists */
-a.forumtitle {
+a.forumtitle,
+a.topictitle {
 	font-family: "Trebuchet MS", Helvetica, Arial, sans-serif;
-	font-size: 1.2em;
+	font-size: 13px;
 	font-weight: bold;
 	text-decoration: none;
 }
@@ -78,10 +77,6 @@ a.forumtitle:hover {
 }
 
 a.topictitle {
-	font-family: "Trebuchet MS", Helvetica, Arial, sans-serif;
-	font-size: 1.2em;
-	font-weight: bold;
-	text-decoration: none;
 	display: inline;
 }
 
@@ -209,5 +204,3 @@ a.feed-icon-forum {
 a.anchor {
 	display: block;
 }
-
-/* stylelint-enable declaration-property-unit-whitelist */
diff --git a/phpBB/styles/prosilver/theme/plupload.css b/phpBB/styles/prosilver/theme/plupload.css
index 3be5663443..7d2c7d9e10 100644
--- a/phpBB/styles/prosilver/theme/plupload.css
+++ b/phpBB/styles/prosilver/theme/plupload.css
@@ -2,11 +2,9 @@
 	$Plupload
 /* -------------------------------------------------------------- */
 
-/* stylelint-disable declaration-property-unit-whitelist */
-
 .attach-panel-multi {
 	display: none;
-	margin-bottom: 1em;
+	margin-bottom: 10px;
 }
 
 .file-list td {
@@ -92,5 +90,3 @@
 	vertical-align: bottom;
 	max-width: 65%;
 }
-
-/* stylelint-enable declaration-property-unit-whitelist */
diff --git a/phpBB/styles/prosilver/theme/print.css b/phpBB/styles/prosilver/theme/print.css
index 753e6bebe5..820256fa98 100644
--- a/phpBB/styles/prosilver/theme/print.css
+++ b/phpBB/styles/prosilver/theme/print.css
@@ -3,8 +3,6 @@
 /* -------------------------------------------------------------- */
 
 /* stylelint-disable selector-max-compound-selectors */
-/* stylelint-disable declaration-property-unit-whitelist */
-/* stylelint-disable declaration-property-unit-blacklist */
 
 /* Lots still TODO here! */
 
@@ -15,7 +13,8 @@
 }
 
 body {
-	font: 11pt Verdana, Arial, Helvetica, sans-serif;
+	font-family: Verdana, Arial, Helvetica, sans-serif;
+	font-size: 14px;
 	color: #000000;
 }
 
@@ -50,7 +49,7 @@ img,
 
 /* Container for the main body */
 .wrap {
-	margin: 0 2em;
+	margin: 0 30px;
 }
 
 p {
@@ -82,25 +81,29 @@ h3 a {
 }
 
 h1 {
-	font-size: 20pt;
+	font-size: 26px;
 }
 
 h2 {
-	font-size: 16pt;
-	margin-top: 1em;
+	font-size: 21px;
+	margin-top: 20px;
 }
 
 h3 {
-	font-size: 14pt;
-	margin-top: 1em;
+	font-size: 18px;
+	margin-top: 20px;
 }
 
 .content {
 	font-family: "Lucida Grande", "Trebuchet MS", Verdana, Arial, Helvetica, sans-serif;
-	font-size: 11pt;
-	line-height: 14pt;
+	font-size: 14px;
+	line-height: 18px;
 	overflow: hidden;
-	margin-bottom: 1em;
+	margin-bottom: 14px;
+}
+
+.postbody .content {
+	font-size: 14px;
 }
 
 /* CSS2 Print tip from: http://www.alistapart.com/articles/goingtoprint/ */
@@ -109,11 +112,9 @@ h3 {
 .postbody a:hover,
 .postbody a:active {
 	font-size: 100%;
-	text-decoration: underline;
 	background: none;
 	color: #666666;
-	margin: -0.1em -0.2em;
-	padding: 0.1em 0.2em;
+	padding: 2px 4px;
 }
 
 html > body .postbody a:link:after,
@@ -132,7 +133,6 @@ hr {
 .author {
 	font-family: Verdana, Arial, Helvetica, sans-serif;
 	font-size: 75%;
-	margin-bottom: 0.6em;
 }
 
 .date {
@@ -153,9 +153,10 @@ html > body .postbody .author a:visited:after,
 html > body .postquote .quote-by a:link:after,
 html > body .postquote .quote-by a:visited:after,
 html > body .postbody h1 a:link:after,
-html > body .postbody h2 a:link:after {
+html > body .postbody h2 a:link:after,
+.post-buttons a:after {
 	text-decoration: none;
-	content: "";
+	content: "" !important;
 }
 
 /* Poster profile */
@@ -171,11 +172,11 @@ html > body .postbody h2 a:link:after {
 .postquote,
 blockquote {
 	font-size: 85%;
-	line-height: 1.5em;
+	line-height: 18px;
 	border: 1px #999999 solid;
 	position: relative;
-	margin: 1em 18% 1em 4%;
-	padding: 0.5em;
+	margin: 12px 154px 12px 34px;
+	padding: 6px;
 }
 
 .postquote img {
@@ -200,7 +201,7 @@ blockquote cite {
 /* List */
 ol,
 ul {
-	margin-left: 15pt;
+	margin-left: 20px;
 }
 
 /* Misc page elements */
@@ -217,12 +218,13 @@ ul {
 	display: none;
 }
 
+/* stylelint-disable declaration-property-unit-whitelist */
 .emoji {
 	width: 1em;
 	min-width: 18px;
 	height: 1em;
 	min-height: 18px;
 }
-/* stylelint-enable selector-max-compound-selectors */
 /* stylelint-enable declaration-property-unit-whitelist */
-/* stylelint-enable declaration-property-unit-blacklist */
+
+/* stylelint-enable selector-max-compound-selectors */
diff --git a/phpBB/styles/prosilver/theme/responsive.css b/phpBB/styles/prosilver/theme/responsive.css
index d1a78cea25..4c4ad63bae 100644
--- a/phpBB/styles/prosilver/theme/responsive.css
+++ b/phpBB/styles/prosilver/theme/responsive.css
@@ -3,8 +3,6 @@
 /* -------------------------------------------------------------- */
 /* stylelint-disable selector-max-compound-selectors */
 /* stylelint-disable selector-no-qualifying-type */
-/* stylelint-disable declaration-property-unit-whitelist */
-/* stylelint-disable declaration-property-unit-blacklist */
 
 @media (max-width: 320px) {
 	select,
@@ -230,7 +228,7 @@
 
 	.site-description h1,
 	.site-description p {
-		line-height: 1.2em;
+		line-height: 24px;
 		text-align: inherit;
 		text-overflow: ellipsis;
 		float: none;
@@ -258,8 +256,8 @@
 	/* Forums and topicslists
 	---------------------------------------------------------------- */
 	li.header dt {
-		font-size: 1.2em;
-		line-height: 1em;
+		font-size: 12px;
+		line-height: 12px;
 		text-align: center;
 		text-transform: none;
 		padding-bottom: 4px;
@@ -591,12 +589,12 @@
 	/* Misc stuff
 	---------------------------------------------------------------- */
 	h2 {
-		margin-top: 0.5em;
+		margin-top: 12px;
 	}
 
 	p {
 		overflow: hidden;
-		margin-bottom: 0.5em;
+		margin-bottom: 8px;
 	}
 
 	p.rightside {
@@ -771,7 +769,7 @@
 @media (max-width: 900px) {
 	.nojs .tabs a span,
 	.nojs .minitabs a span {
-		letter-spacing: -0.5px;
+		letter-spacing: -0.03em;
 		text-overflow: ellipsis;
 		overflow: hidden;
 		max-width: 40px;
@@ -834,5 +832,3 @@
 
 /* stylelint-enable selector-max-compound-selectors */
 /* stylelint-enable selector-no-qualifying-type */
-/* stylelint-enable declaration-property-unit-whitelist */
-/* stylelint-enable declaration-property-unit-blacklist */