I made a few customizations on Nuget and I want to install my extension on Visual Web Developer Express 2010, but it seems that the source that i downloaded is not prepared for that. I noticed that the file source.extension.vsixmanifest does not contain the entries for the express version. What am i doing wrong?

You're not doing anything wrong. This is not a supported scenario. The VSIX that you build can only be installed into Visual Studio. Only the VSIX that is built by Microsoft can be installed into VWD.

Ok, thank you very much!

Coming back with another question: the extension i built does not work because is not signed by Microsoft or the extension for Web Developer is totally different?

The extension that is available via the Extension Manager is a rebranded vsix that is designed to be installable in specific Express SKUs. Part of this involves signing the vsix and the binaries.

Thanks for the help.

So there is no way to make my extension work on VWD? Even if I sign it?

Not that I know of. If these changes make sense for the general NuGet audience, you might want to start a discussion \ send a pull request. That way it would be part of our regular releases.