However that example is bad as line-height should never be applied using absolute units such as points or pixels. In the prior example, when text is resized in a browser, the font-size increases (to 18 pt for example) but the line-height may remain at 15 pt. So instead of the lines being spaced apart, they would actually overlap.
That example will give you the same line-height throughout all your paragraphs, however it does introduce the danger that, when the browser text size is increased by your reader (to 18 pt for example) the line-height may remain at 15 pt. The result being that, instead of the lines being spaced apart, they would actually overlap.
-A better approach is to use a unitless value. The preceding example could also be coded as:
+A safer approach is to use a unitless value. The preceding example could also be coded as:
p {
font-size: 12pt;