Struggling to get postbacks to fire using IE11?
Tried forcing the compatibility mode using meta tags to no avail?
Your website only works in IE11 when add the url to the compatibility view settings list?
I feel your pain so read on…

The reason for all these problems with IE11 lies in the user agent string. The new default user agent string is “Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko”. Microsoft changed this so UA-string sniffing logic would interpret the site as either Gecko or WebKit. Previous versions of the string would be something like: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0), notice the MSIE token! By adding your url to the compatibility view settings list IE would add the MSIE token back into the string.

Ok so now you want to do it in code…

The solution is to create a new folder in your website named “App_Browsers”. Within this folder add this file (ie.browser) and voila your site will start working as expected using IE11.

This trick is basically shipping a browser definition file with your website, rather than altering the definition files buried in the ISS framework installation on your server.