well.i updated the version in web.config to 2.0 and i passed this issue. but i do not understand why nop.web.framework and nop.web are using different versions ...
I had the same problem, but for ver 2.4. This is what I did to get it working;
1.In Solution Explorer, right-click Nop.Web.Framework and then select Unload Project. Then right-click the name again and select Edit Nop.Web.Framework .csproj.
2.Locate the following assembly references:
<Reference Include="System.Web.WebPages"/> <Reference Include="System.Web.Helpers" /> Replace them with the following: <Reference Include="System.Web.WebPages, Version=1.0.0.0,Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL "/> <Reference Include="System.Web.Helpers, Version=1.0.0.0,Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL" />
3.Save the changes, close the project file you were editing, and then right-click the project and select Reload.
4. Repeat for Nop.Web project.
5. Make sure the solution startup project is set to Nop.Web (after you unload the project VS may change the startup project).