In an answer about CSS, a user said:
Internet Explorer
hasis said to have a limit of 4096 CSS rules per file. ReferenceAlso, it has a limit on the number of style sheets you can embed in a single document. I think it is 20.
While the reference on MSDN seems to confirm this (and there's a blog post which confirms this in IE7), is this still the case for IE8?
Yes, IE8 (and even IE9 apparently) limit the number of style sheets to 31 per page.
Telerik has an article and test page which demonstrate the issue. According to comments in the same article, the 4096 rules per file limitation has been marked as Won't Fix in Microsoft Connect but I've been unable to verify that.