From time to time I see posts like this describing "CSS Hacks" to detect a particular version of IE. This post describes how removing conditional comments support in IE10 might be a problem for targeting workarounds to IE10. Specifically it says: "But without conditional comments in IE10, the only options we’re left with to target CSS problems are hacks or browser sniffing — and we certainly don’t want to resort to the latter." It goes on to describe a set of hacks that amount to browser sniffing using JavaScript (if (/*@cc_on!@*/false && document.documentMode === 10)) or some combination...

Scott Hanselman describes the ASP.NET fix need to make the browser definition files work with IE10. In general we encourage developers to use feature detection when switching their mark-up but the ASP.NET infrastructure has been around for a long time. One thing to watch out for if you are doing custom browser detection is the two digit version number with IE10. We've seen a few sites have issues because they only expect a single digit and end up thinking IE10 is IE1.