I am looking to develop an application that basically allows users to annotate web content. I mean something like what iMarkup does. What it does is, (if I understand correctly) that it places an overlay on the web content, and allows the user to select a pen from a menu and write freeform on the "canvas", and saves the same. When the same webpage is reopened on a later date it basically restores the annotations.
I am stymied here, I have no idea how to progress and which technologies to use. I have a basic understanding that the same is done with the aid of DOM, and DHTML, but I dont quite know what how. IMarkup installs an activeX component, but I would like to make it possible for the same application to be used on Firefox as well... so activeX is out.
Any help would be greatly appreciated.