>>I recently had an issue with an ASP.NET site not rendering properly on a Windows 2003 server only for IE11. I was able to resolve it adding the browser file indicated in the last answer at http://stackoverflow.com/questions/17417420/app-browsers-definition-file-for-ie-11.
>
>Is this a file that has to be dropped on the server?
>
>I verified and this is IE related only. I tried with other browsers and the focus appears ok.
>
>I certainly hope a fix in upcoming updates will adjust that.

See the remarks section at http://msdn.microsoft.com/en-us/library/ms228122%28v=vs.100%29.aspx

The following resources may also help, although they primarily relate to IE10:
http://stackoverflow.com/questions/6983732/ie10-user-agent-causes-asp-net-to-not-send-back-set-cookie-ie10-not-setting-coo
http://connect.microsoft.com/VisualStudio/feedback/details/662275/asp-net-user-agent-sniffing-and-ie10-internet-explorer-10
http://support.microsoft.com/kb/2600088
http://support.microsoft.com/kb/2600217
http://www.hanselman.com/blog/BugAndFixASPNETFailsToDetectIE10CausingDoPostBackIsUndefinedJavaScriptErrorOrMaintainFF5ScrollbarPosition.aspx