Assembly error

 Error 4 The type 'ASP.aspx_controls_maintop_ascx' exists in both 'c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\online_store\7e5e2cc2\6d0e9d9d\App_Web_iv00njwa.dll' and 'c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\online_store\7e5e2cc2\6d0e9d9d\App_Web_ndsosjuw.dll' D:\Projects\Online_Store\aspx\Confirm.aspx

If you get error like this that 2 assemblies exists in same path then go to the specified path 

c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\

and delete ur project.

Because this is all temporary files and restart ur visual studio.