could not load type 'assembly name' error in IIS handler mapping

Hello IIS experts

I added one module using .net framework visualstdio2010 and I added handler mapping to application .while browsing it shows the error

"could not load type' myassembly name'  .what might be the reason for such error .In handler mapping I gave the path like 'namespace.classname" ,is it right way or some other causes this error.can any one suggest help ful.

Thanks and regards

Muralikrishna