In an answer about CSS, a user said:
Internet Explorer
hasis said to have a limit of 4096 CSS rules per file. Reference
I was building a site and hit this issue myself. It was driving me batty until a co-worker pointed this 31 CSS files issue out. Looking into it what struck me that it's more complicated than that because IE8 seemed to be loading some of the styles from the sheet but not all of them. It was ignoring media queries and chained classes just like it was behaving in Quirks mode — even though it wasn't in Quirks mode and both those were in the same CSS file as other CSS that was being used. Once I aggregated the CSS files into one file it all worked fine. Anyway I just wanted to point out that somehow this 31 limit also seems to trigger something like Quirks mode.