diff --git a/.postcss-sorting.json b/.postcss-sorting.json
index a1bc5ff1ae..11a55f3c3d 100644
--- a/.postcss-sorting.json
+++ b/.postcss-sorting.json
@@ -2,12 +2,16 @@
 	"order": [
 		"custom-properties",
 		"dollar-variables",
+		{
+			"type": "at-rule",
+			"name": "include"
+		},
 		"declarations",
+		"rules",
 		{
 			"type": "at-rule",
 			"name": "media"
-		},
-		"rules"
+		}
 	],
 	"properties-order": [
 		{
@@ -70,12 +74,7 @@
 				"background-origin",
 				"background-size",
 				"interpolation-mode",
-				"filter"
-			]
-		},
-		{
-			"emptyLineBefore": false,
-			"properties": [
+				"filter",
 				"border",
 				"border-width",
 				"border-style",
diff --git a/.stylelintrc b/.stylelintrc
index 160816a389..4740068395 100644
--- a/.stylelintrc
+++ b/.stylelintrc
@@ -18,12 +18,11 @@
 			}
 		],
 		"block-closing-brace-newline-before": "always-multi-line",
-		"block-closing-brace-space-after": "always-single-line",
 		"block-closing-brace-space-before": "always-single-line",
 
 		"block-no-empty": true,
 
-		"block-opening-brace-newline-after": "always",
+		"block-opening-brace-newline-after": "always-multi-line",
 		"block-opening-brace-space-after": "always-single-line",
 		"block-opening-brace-space-before": "always",
 
@@ -131,6 +130,11 @@
 		"property-case": "lower",
 		"property-no-unknown": true,
 
+		"rule-empty-line-before": ["always-multi-line", {
+			"ignore": ["after-comment"],
+			"except": ["first-nested"]
+		}],
+
 		"selector-attribute-brackets-space-inside": "never",
 		"selector-attribute-operator-space-after": "never",
 		"selector-attribute-operator-space-before": "never",
@@ -179,12 +183,16 @@
 		"order/declaration-block-order": [
 			"custom-properties",
 			"dollar-variables",
+			{
+				"type": "at-rule",
+				"name": "include"
+			},
 			"declarations",
+			"rules",
 			{
 				"type": "at-rule",
 				"name": "media"
-			},
-			"rules"
+			}
 		],
 		"order/declaration-block-properties-specified-order": [
 			[
diff --git a/phpBB/styles/prosilver/theme/colours.css b/phpBB/styles/prosilver/theme/colours.css
index f740dafb2c..f5b0211f03 100644
--- a/phpBB/styles/prosilver/theme/colours.css
+++ b/phpBB/styles/prosilver/theme/colours.css
@@ -161,10 +161,6 @@ ul.zebra-list li:nth-child(even) {
 	background-color: #e7e8ea;
 }
 
-.site_logo {
-	background-image: url("./images/site_logo.gif");
-}
-
 /* horizontal lists */
 
 ul.navlinks {
@@ -336,9 +332,8 @@ p.post-notice {
 	------------------------------------------------------------- */
 
 ul.forums {
-	background-color: #eef5f9; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to bottom, #d2e0eb 0%, #eef5f9 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#d2e0eb", endcolorstr="#eef5f9", gradienttype=0); /* ie6-9 */
+	background-color: #eef5f9;
+	background-image: linear-gradient(to bottom, #d2e0eb 0%, #eef5f9 100%);
 }
 
 ul.topiclist li {
@@ -594,10 +589,6 @@ fieldset.polls dd div {
 	color: #000000;
 }
 
-.online {
-	background-image: url("./en/icon_user_online.gif");
-}
-
 dd.profile-warnings {
 	color: #bc2a4d;
 }
@@ -627,9 +618,8 @@ dd.profile-warnings {
 /*	colours and backgrounds for buttons.css
 	------------------------------------------------------------- */
 .button {
-	background-color: #e9e9e9; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to bottom, #ffffff 0%, #e9e9e9 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#ffffff", endcolorstr="#e9e9e9", gradienttype=0); /* ie6-9 */
+	background-color: #e9e9e9;
+	background-image: linear-gradient(to bottom, #ffffff 0%, #e9e9e9 100%);
 	border-color: #c7c3bf;
 	-webkit-box-shadow: 0 0 0 1px #ffffff inset;
 	box-shadow: 0 0 0 1px #ffffff inset;
@@ -638,9 +628,8 @@ dd.profile-warnings {
 
 .button:hover,
 .button:focus {
-	background-color: #ffffff; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to bottom, #e9e9e9 0%, #ffffff 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#e9e9e9", endcolorstr="#ffffff", gradienttype=0); /* ie6-9 */
+	background-color: #ffffff;
+	background-image: linear-gradient(to bottom, #e9e9e9 0%, #ffffff 100%);
 	border-color: #0a8ed0;
 	text-shadow: 1px 1px 0 #ffffff, -1px -1px 0 #ffffff, -1px -1px 0 rgba(188, 42, 77, 0.2);
 }
@@ -743,244 +732,78 @@ dd.profile-warnings {
 	box-shadow: 0 0 10px #0075b0;
 }
 
-/* icon images */
 
-.contact-icon {
-	background-image: url("./images/icons_contact.png");
-}
+.site_logo { background-image: url("./images/site_logo.gif"); }
+.contact-icon { background-image: url("./images/icons_contact.png"); }
 
-/* profile & navigation icons */
-.pm-icon {
-	background-position: 0 0;
-}
-
-.email-icon {
-	background-position: -21px 0;
-}
-
-.jabber-icon {
-	background-position: -80px 0;
-}
-
-.phpbb_icq-icon {
-	background-position: -61px 0;
-}
-
-.phpbb_wlm-icon {
-	background-position: -182px 0;
-}
-
-.phpbb_aol-icon {
-	background-position: -244px 0;
-}
-
-.phpbb_website-icon {
-	background-position: -40px 0;
-}
-
-.phpbb_youtube-icon {
-	background-position: -98px 0;
-}
-
-.phpbb_facebook-icon {
-	background-position: -119px 0;
-}
-
-.phpbb_googleplus-icon {
-	background-position: -140px 0;
-}
-
-.phpbb_skype-icon {
-	background-position: -161px 0;
-}
-
-.phpbb_twitter-icon {
-	background-position: -203px 0;
-}
-
-.phpbb_yahoo-icon {
-	background-position: -224px 0;
-}
+/* profile icons */
+.online { background-image: url("./en/icon_user_online.gif"); }
+.pm-icon { background-position: 0 0; }
+.email-icon { background-position: -21px 0; }
+.jabber-icon { background-position: -80px 0; }
+.phpbb_icq-icon { background-position: -61px 0; }
+.phpbb_wlm-icon { background-position: -182px 0; }
+.phpbb_aol-icon { background-position: -244px 0; }
+.phpbb_website-icon { background-position: -40px 0; }
+.phpbb_youtube-icon { background-position: -98px 0; }
+.phpbb_facebook-icon { background-position: -119px 0; }
+.phpbb_googleplus-icon { background-position: -140px 0; }
+.phpbb_skype-icon { background-position: -161px 0; }
+.phpbb_twitter-icon { background-position: -203px 0; }
+.phpbb_yahoo-icon { background-position: -224px 0; }
 
 /* forum icons & topic icons */
-.global_read {
-	background-image: url("./images/announce_read.gif");
-}
+.global_read { background-image: url("./images/announce_read.gif"); }
+.global_read_mine { background-image: url("./images/announce_read_mine.gif"); }
+.global_read_locked { background-image: url("./images/announce_read_locked.gif"); }
+.global_read_locked_mine { background-image: url("./images/announce_read_locked_mine.gif"); }
+.global_unread { background-image: url("./images/announce_unread.gif"); }
+.global_unread_mine { background-image: url("./images/announce_unread_mine.gif"); }
+.global_unread_locked { background-image: url("./images/announce_unread_locked.gif"); }
+.global_unread_locked_mine { background-image: url("./images/announce_unread_locked_mine.gif"); }
 
-.global_read_mine {
-	background-image: url("./images/announce_read_mine.gif");
-}
+.announce_read { background-image: url("./images/announce_read.gif"); }
+.announce_read_mine { background-image: url("./images/announce_read_mine.gif"); }
+.announce_read_locked { background-image: url("./images/announce_read_locked.gif"); }
+.announce_read_locked_mine { background-image: url("./images/announce_read_locked_mine.gif"); }
+.announce_unread { background-image: url("./images/announce_unread.gif"); }
+.announce_unread_mine { background-image: url("./images/announce_unread_mine.gif"); }
+.announce_unread_locked { background-image: url("./images/announce_unread_locked.gif"); }
+.announce_unread_locked_mine { background-image: url("./images/announce_unread_locked_mine.gif"); }
 
-.global_read_locked {
-	background-image: url("./images/announce_read_locked.gif");
-}
+.forum_link { background-image: url("./images/forum_link.gif"); }
+.forum_read { background-image: url("./images/forum_read.gif"); }
+.forum_read_locked { background-image: url("./images/forum_read_locked.gif"); }
+.forum_read_subforum { background-image: url("./images/forum_read_subforum.gif"); }
+.forum_unread { background-image: url("./images/forum_unread.gif"); }
+.forum_unread_locked { background-image: url("./images/forum_unread_locked.gif"); }
+.forum_unread_subforum { background-image: url("./images/forum_unread_subforum.gif"); }
 
-.global_read_locked_mine {
-	background-image: url("./images/announce_read_locked_mine.gif");
-}
-
-.global_unread {
-	background-image: url("./images/announce_unread.gif");
-}
-
-.global_unread_mine {
-	background-image: url("./images/announce_unread_mine.gif");
-}
-
-.global_unread_locked {
-	background-image: url("./images/announce_unread_locked.gif");
-}
-
-.global_unread_locked_mine {
-	background-image: url("./images/announce_unread_locked_mine.gif");
-}
-
-.announce_read {
-	background-image: url("./images/announce_read.gif");
-}
-
-.announce_read_mine {
-	background-image: url("./images/announce_read_mine.gif");
-}
-
-.announce_read_locked {
-	background-image: url("./images/announce_read_locked.gif");
-}
-
-.announce_read_locked_mine {
-	background-image: url("./images/announce_read_locked_mine.gif");
-}
-
-.announce_unread {
-	background-image: url("./images/announce_unread.gif");
-}
-
-.announce_unread_mine {
-	background-image: url("./images/announce_unread_mine.gif");
-}
-
-.announce_unread_locked {
-	background-image: url("./images/announce_unread_locked.gif");
-}
-
-.announce_unread_locked_mine {
-	background-image: url("./images/announce_unread_locked_mine.gif");
-}
-
-.forum_link {
-	background-image: url("./images/forum_link.gif");
-}
-
-.forum_read {
-	background-image: url("./images/forum_read.gif");
-}
-
-.forum_read_locked {
-	background-image: url("./images/forum_read_locked.gif");
-}
-
-.forum_read_subforum {
-	background-image: url("./images/forum_read_subforum.gif");
-}
-
-.forum_unread {
-	background-image: url("./images/forum_unread.gif");
-}
-
-.forum_unread_locked {
-	background-image: url("./images/forum_unread_locked.gif");
-}
-
-.forum_unread_subforum {
-	background-image: url("./images/forum_unread_subforum.gif");
-}
-
-.sticky_read {
-	background-image: url("./images/sticky_read.gif");
-}
-
-.sticky_read_mine {
-	background-image: url("./images/sticky_read_mine.gif");
-}
-
-.sticky_read_locked {
-	background-image: url("./images/sticky_read_locked.gif");
-}
-
-.sticky_read_locked_mine {
-	background-image: url("./images/sticky_read_locked_mine.gif");
-}
-
-.sticky_unread {
-	background-image: url("./images/sticky_unread.gif");
-}
-
-.sticky_unread_mine {
-	background-image: url("./images/sticky_unread_mine.gif");
-}
-
-.sticky_unread_locked {
-	background-image: url("./images/sticky_unread_locked.gif");
-}
-
-.sticky_unread_locked_mine {
-	background-image: url("./images/sticky_unread_locked_mine.gif");
-}
-
-.topic_moved {
-	background-image: url("./images/topic_moved.gif");
-}
+.sticky_read { background-image: url("./images/sticky_read.gif"); }
+.sticky_read_mine { background-image: url("./images/sticky_read_mine.gif"); }
+.sticky_read_locked { background-image: url("./images/sticky_read_locked.gif"); }
+.sticky_read_locked_mine { background-image: url("./images/sticky_read_locked_mine.gif"); }
+.sticky_unread { background-image: url("./images/sticky_unread.gif"); }
+.sticky_unread_mine { background-image: url("./images/sticky_unread_mine.gif"); }
+.sticky_unread_locked { background-image: url("./images/sticky_unread_locked.gif"); }
+.sticky_unread_locked_mine { background-image: url("./images/sticky_unread_locked_mine.gif"); }
 
 .pm_read,
-.topic_read {
-	background-image: url("./images/topic_read.gif");
-}
-
-.topic_read_mine {
-	background-image: url("./images/topic_read_mine.gif");
-}
-
-.topic_read_hot {
-	background-image: url("./images/topic_read_hot.gif");
-}
-
-.topic_read_hot_mine {
-	background-image: url("./images/topic_read_hot_mine.gif");
-}
-
-.topic_read_locked {
-	background-image: url("./images/topic_read_locked.gif");
-}
-
-.topic_read_locked_mine {
-	background-image: url("./images/topic_read_locked_mine.gif");
-}
+.topic_read { background-image: url("./images/topic_read.gif"); }
+.topic_moved { background-image: url("./images/topic_moved.gif"); }
+.topic_read_mine { background-image: url("./images/topic_read_mine.gif"); }
+.topic_read_hot { background-image: url("./images/topic_read_hot.gif"); }
+.topic_read_hot_mine { background-image: url("./images/topic_read_hot_mine.gif"); }
+.topic_read_locked { background-image: url("./images/topic_read_locked.gif"); }
+.topic_read_locked_mine { background-image: url("./images/topic_read_locked_mine.gif"); }
 
 .pm_unread,
-.topic_unread {
-	background-image: url("./images/topic_unread.gif");
-}
-
-.topic_unread_mine {
-	background-image: url("./images/topic_unread_mine.gif");
-}
-
-.topic_unread_hot {
-	background-image: url("./images/topic_unread_hot.gif");
-}
-
-.topic_unread_hot_mine {
-	background-image: url("./images/topic_unread_hot_mine.gif");
-}
-
-.topic_unread_locked {
-	background-image: url("./images/topic_unread_locked.gif");
-}
-
-.topic_unread_locked_mine {
-	background-image: url("./images/topic_unread_locked_mine.gif");
-}
-
+.topic_unread { background-image: url("./images/topic_unread.gif"); }
+.topic_unread_mine { background-image: url("./images/topic_unread_mine.gif"); }
+.topic_unread_hot { background-image: url("./images/topic_unread_hot.gif"); }
+.topic_unread_hot_mine { background-image: url("./images/topic_unread_hot_mine.gif"); }
+.topic_unread_locked { background-image: url("./images/topic_unread_locked.gif"); }
+.topic_unread_locked_mine { background-image: url("./images/topic_unread_locked_mine.gif"); }
 
 /*	colours and backgrounds for cp.css
 	------------------------------------------------------------- */
@@ -1030,9 +853,8 @@ ul.cplist {
 
 .tabs .activetab > a,
 .tabs .activetab > a:hover {
-	background-color: #cadceb; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to bottom, #e2f2ff 0%, #cadceb 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#e2f2ff", endcolorstr="#cadceb", gradienttype=0); /* ie6-9 */
+	background-color: #cadceb;
+	background-image: linear-gradient(to bottom, #e2f2ff 0%, #cadceb 100%);
 	border-color: #cadceb;
 	box-shadow: 0 1px 1px #f2f9ff inset;
 	color: #333333;
@@ -1066,27 +888,23 @@ ul.cplist {
 
 /* link styles for the sub-section links */
 .navigation a {
-	background: #cadceb; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to right, #b4c4d1 50%, #cadceb 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#b4c4d1", endcolorstr="#cadceb", gradienttype=1); /* ie6-9 */
+	background: #cadceb;
+	background-image: linear-gradient(to right, #b4c4d1 50%, #cadceb 100%);
 	color: #333333;
 }
 
 .rtl .navigation a {
-	background: #b4c4d1; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to right, #cadceb 50%, #b4c4d1 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#cadceb", endcolorstr="#b4c4d1", gradienttype=1); /* ie6-9 */
+	background: #b4c4d1;
+	background-image: linear-gradient(to right, #cadceb 50%, #b4c4d1 100%);
 }
 
 .navigation a:hover {
 	background: #aabac6;
-	filter: progid:dximagetransform.microsoft.gradient(enabled = false);
 	color: #bc2a4d;
 }
 
 .navigation .active-subsection a {
 	background: #f9f9f9;
-	filter: progid:dximagetransform.microsoft.gradient(enabled = false);
 	color: #d31141;
 }
 
@@ -1310,9 +1128,8 @@ input.disabled {
 }
 
 .dropdown-extended .header {
-	background-color: #f1f8ff; /* old browsers */ /* ff3.6+ */
-	background-image: linear-gradient(to bottom, #f1f8ff 0%, #cadceb 100%); /* w3c */
-	filter: progid:dximagetransform.microsoft.gradient(startcolorstr="#f1f8ff", endcolorstr="#cadceb", gradienttype=0); /* ie6-9 */
+	background-color: #f1f8ff;
+	background-image: linear-gradient(to bottom, #f1f8ff 0%, #cadceb 100%);
 }
 
 .dropdown .pointer {
@@ -1361,4 +1178,7 @@ li.notification-disapproved strong {
 	background-color: #d31141;
 	color: #ffffff;
 }
-/* stylelint-enable */
+
+/* stylelint-enable selector-max-compound-selectors */
+/* stylelint-enable selector-no-qualifying-type */
+/* stylelint-enable no-indistinguishable-colors */