This is a strange message actually. You’re not supposed to see this, unless someone tinkers with the web.config file of your application.
What this message means is that the debug=true command is missing from your web.config file (or, it was somehow removed). to resolve, locate the line that refers to the compilation and change to (or, create if you don’t have one):
<compilation debug=”true” defaultLanguage=”c#” />
Make sure to change the defaultLanguage directive to match the language your application works with.
You can actually search for the word “compilation” in your web.config. The reason this would be useful is that depending on your configuration, the tag structure may be different. You may find this instead:
<compilation batch=”false” debug=”false”></compilation>
In this case too, just change the debug value to “true”.
