Google Chrome's extensions are purely based on HTML, CSS and some custom Javascript. That's incredibly limiting, especially when you're talking about UI manipul

Google Chrome's extensions are purely based on HTML, CSS and some custom Javascript. That's incredibly limiting, especially when you're talking about UI manipulation. When you're creating Firefox extensions, you're writing the same native language (XUL) that the Firefox developers use to add features to Firefox itself. Chrome's extensions only have similar capabilities as Mozilla JetPacks have.