Registering Custom HttpModule in IIS7 Web.config

I’ve been writing an Error Hander HttpModule for a current ASP.NET WebForm project and things were going well until my last merge with TFS. All of a sudden, my HttpModule wouldn’t register anymore. For the life of me I couldn't’ figure out what had changed. I spent half the day trying to figure out what in the world was going on. Here is the chain of events that I tried before finding the actual solution. If you want, you can just skip to the end to find the answer :)