This is something I am not aware of, not even thought it makes any sense. Internet Explorer, version 6 to 9, does have some limitation to include CSS files. It only allows as much as 31 files to be included in a page.
Eric Law went to explain why this is the case. The limitation has to do with IE using 32bit integer to identify these stylesheets rules.
However, this is not an issue in IE 10.