Recently we had an HTML form that took a username and password to pass through to a silverlight web app. Using internet explorer when trying to log in , the form would refresh with no error message not log the user in. However the login worked internally fine….

Internet Explorer can detect if a website is internal through the IP address and automatically puts them in “Compatibility View” through the default Compatibility View Settings. As soon as we force the external IE client to use Compatibility it worked. We added this Meta Tag in the IIS Settings

<meta http-equiv=”X-UA-Compatible” content=”IE=EmulateIE7″ />

( Can be added to HTML as well ) which forced compatibility mode for External users as well ( No need to add the site manually )

However there was still a problem with Internet Explorer 10 not using this meta tag

Briefly, the issue is because that Asp.net doesn’t return Set-Cookie properly if the user agent sent in http request is IE10. It works for compatibility mode because the user agent will be set as IE7.

Thanks to http://www.hanselman.com/blog/BugAndFixASPNETFailsToDetectIE10CausingDoPostBackIsUndefinedJavaScriptErrorOrMaintainFF5ScrollbarPosition.aspx

Basically, what we need to do is to download and install some Microsoft hotfix. .NET 4 – http://support.microsoft.com/kb/2600088 .NET 2.0 http://support.microsoft.com/kb/2600100 for Win7 SP1/Windows Server 2008 R2 SP1, Windows Vista/Server 2008, Windows XP/Server 2003 http://support.microsoft.com/kb/2608565 for Win7/Windows Server 2008 R2 RTM

What the fixes do is update the ie.browser and firefox.browser files in \Windows\Microsoft.NET\Framework\<version>\Config\Browsers with new and future-proofed versions of these browser definitions. Nothing else is affected.

From the description of the blog, the patch is very safe to run its only job is updating several browser-sniffing related files (very small changes).