Comment 16 for bug 1086550

Ah, IE: http://msdn.microsoft.com/en-us/library/ie/cc304078%28v=vs.85%29.aspx says "In Windows Internet Explorer 8, as well as later versions of Windows Internet Explorer in IE8 Standards mode, only the one-colon form of this pseudo-element is recognized—that is, :before.

Beginning with Windows Internet Explorer 9, the ::before pseudo-element requires two colons, though the one-colon form is still recognized and behaves identically to the two-colon form. Microsoft and the World Wide Web Consortium (W3C) encourage web authors to use the two-colon form of the ::before pseudo-element".