My application is a dotnet 4 hybrid - MVC in some areas, web forms in others. This application was recently upgraded to dotnet 4 and includes a lot of older code and some mismatched parts. Unfortunately it includes a telerik component that requires me to run the Application pool in classic mode. In order to fix this (in IIS7) I have to add a handler mapping to the IIS configuration. This mapping is basically a wildcard mapping that points the wildcard path "*" to the %windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll. The problem I am running into is this: For some reason this mapping gets dropped when deploying the site. So, can I add the functionality of this mapping to the web config? If so, How? Or is there another solution to make this manually added mapping "sticky" so that it remains in place during and after a deployment? (I am also asking this on StackOverflow, as I'm not sure if this should be a coding question or a Server question)