Cannot refer to BLL and DAL from a Project?

I have written BLL and DLL classes under a project called Library; I have also a
Web app under a project called Webapp. These two projects are under a Solution
called MySolution.

I seem to have problem in getting my Web app. in the Webapp project to refer to
a class in the Library project, even though I have add reference to Library
project in the Webapp project. 

 Any idea what is wrong?  Your suggestion will be much appreciated. Thanks in
advance.

sg2000

Have you included an Imports (vb) or Using (C#) statement at the top of the
class that uses the referenced libraries?

Thanks very much TGnat for the quick and very helpful response. Yes, somehow I
forgot to include "Using Library; " on my Web app. The Web app now
works perfectly. Thanks again.

sg2000