Abstract: An annotation structure for web pages, a system and a method for annotating web pages are disclosed. In the invention, a web page displayed by a web browser is treated as a bottom web page, and an XML-based vector graphic annotation is overlaid on the bottom web page, wherein the XML-based vector graphic annotation includes annotation layers created by users. All users can create their respective annotation layer on the same bottom web page, edit various annotation objects on their own annotation layer, and save the edited annotation objects onto their respective annotation layer, wherein the annotation objects are XML-based vector graphic elements having better controllability. This will constitute multiple vector graphic annotation layers on the bottom web page. When sharing, the user only needs to transmit the address (e.g. URL) of the bottom web page and his own annotation layer to other users.