Originally posted at http://timcosgrove.net ; content re-posted by author
I ran across this today: apparently, Internet Explorer (all versions, not just IE 6) can only render a total of 4095 selectors from an external CSS file. After that, it simply starts ignoring the selectors. If you don't believe me, see the CSS rendering errors for yourself (only visible in IE, all versions).
This has been remarked on before, but it's definitely not common knowledge: