Bookmark of “IE9 :before font-size bug”

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Seems there's a bug in Internet Explorer 9 wherein pseudo content (:before and :after content) doesn't get parsed properly in the DOM, so instead of declarations like font-size being applied only once despite multiple occurrences of the rule, but is in fact treated like a child element in each instance.

From what I’ve read, this bug can be avoided by using px instead of em units.