Handler "ExtensionlessUrlHandler-Integrated-4.0" has a bad module "ManagedPipelineHandler" in its module list
Try to re-register ASP.NET with aspnet_regiis -i. It worked for me.
A likely path for .NET 4 (from elevated command prompt):
c:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -i
If you're running into this error with Windows 8/Windows Server 2012 and .Net 4.5 follow these instructions here:http://www.britishdeveloper.co.uk/2013/01/handler-extensionlessurlhandler.html
Go to "turn Windows features on or off"Then Internet Information ServicesThen World Wide Web ServicesThen Application Development FeaturesAnd then enable ASP.NET 4.5
This worked for me (although the wizard and wording is a little different in Windows Server 2012, but you'll figure it out). With this being said, why this is necessary after installing everything through the Web Platform Installer including all of the dependencies is completely beyond me...
Despite following most of the advice on this page, I was still getting problems on Windows Server 2012. Installing .NET Extensibility 4.5 solved it for me:
Add Roles and Features > Server Roles > Web Server (IIS) > Web Server > Application Development > .NET Extensibility 4.5