ASP.NET Custom 404 page not returning 404 code

After trying to setup my site for Google Webmaster Tools I found that my custom ASP.NET 404 page was not returning the 404 status code. The problem lies in the fact that my custom 404 page is a content form that uses a master page. The master page will override the content form status code. It displayed the correct custom page and told the browser that everything is OK (Code 200). This is considered a soft 404 or false 404. Google doesn't like this. I found many articles on the issue but the solution I want didn't seem to work. More...