Today I had a weird problem, as Internet Explorer (who else could it be) was not loading my CSS file and the website was not displaying any style at all in that browser. After checking here and there, it seems IE only loads the first 31 CSS files you have and not the rest.
Luckyly I was not really trying to load that many style sheets, as by accident a folder with jQuery demos was included in the project App_Themes folder and that loaded many sheets for the different demos. Once the jQuery demos folder was removed the page worked nice.
Warning: If you were releasing in a development server you may need to remove all the files manually before releasing again.