ASP .NET 4.0 and IIS 6.0

While doing some work today that involved installing the .NET 4.0 Framework onto Windows Server 2003 then upgrading a web app to use the new framework, I ran into a problem where I would receive 404 Page Not Found errors when trying to load the updated webpages with a browser.  
What I found is that ASP.NET 4.0 doesn't get automatically approved for use within IIS 6.0.  So, to fix, follow the below to allow the ASP.NET v4.0.30319 web service extension

1. Open Internet Information Services (IIS) Manager
2. Expand ServerName on the left
3. Click Web Service Extensions on the left
4. Click ASP.NET v4.0.30319 on the right
5. Click ‘Allow’