I was able to find this on google and it fixed the problem. Other sites suggested several web.config changes etc. This suggestion worked for me so I wanted to pass it on especially since this error can drive one crazy!!!
Here's the link I found this solution at:
. See the response at 1:44 by ScottGu...
The problem you are having above is that the "/foldername
" directory is not marked as an application, yet the \bin directory containing your assemblies is probably contained underneath it. As such, ASP.NET isn't looking for your assembly in the right place -- instead it is looking for it in the \bin directory underneath the root site/application on your system (note how the error message above starts with the text "Server Error in '/' Application").
To fix this, you should go into the IIS admin tool, right click on the /foldername
directory and pull up its properties. You'll then want to make it as an application within IIS (by clicking the "create" button). The assemblies in the \bin directory should then resolve correctly.