Web application doesnt work in 2005

[Juna]

I have been working in vs2003, but now started to work in
vs2005 but the problem,
I have simple web application not website, which work i mean open in
browser when we press F5 or run the application by pressing run button.
but it doesnt work when we type the path directly in the browser's
address bar eg. http://localhost/testapplicationdefault.aspx
error it gives is "COULD NOT LOAD testapplication._default". IN
default.aspx.
While in 2003 this work fine.
Why is this happening, and while i create website in http it doesnt
allow to debug the application.ie it doesnt work when i press F5 or try
to run by pressing run button.
Can any one give me the solution.

Thanks
Prajesh Shrestha.