Help in Creating C# Class Library (DLL) Using Visual Studio .NET

Question

hi
the article regarding Creating C# Class Library (DLL) Using Visual Studio .NET was very simple and clear in the case of console applications but i am finding error when i try to implement it in web application.
 
the error was "missing the assembly" after adding reference i would find the namespace in the solution explorer but when i build and run, i am getting the error
pls help me, is there any other method for adding reference in web application
 
thanxs and regards
Aarthi