Symptoms
When using VS.NET Web Developer Express Edition, you may have a site that compiles fine in the development environment but fails when you copy it to the local IIS server.
Cause
ASP.NET 2.0 is not the default .NET version used by IIS.? It works in the development environment because VS.NET compiles a virtual web server with the proper .NET version before code compilation begins.
Thinking it occurred because the virtual directory wasn't identified as an application, I created a site (called personal) that mapped to the directory I copied, but still failed.
As it turns out, 'xmlns' is a component in ASP.NET 2.0, and will generate that error when compiled on an IIS server running ASP.NET 1.1.? This is delightfully easy to fix:
Your page should now work.