I am obliged to say I'm not a coder, but the idea might still be useful if it hasn't been implemented yet, if there is enough interest for it and if someone is willing to implement it.

The idea is a firefox extension which would allow you to make scribbles or quick notes over the web page you're viewing. You select any element, usually text, right click and choose to add a scribble and it gets added to the page by modifying its output to add a little icon after the selected element which reveals your scribble once clicked. Editing the page like this is possible as greasemonkey plugin proves, but such extension would be different from greasemonkey in that there is a specific use case for which it is designed for. I know I can edit any page with greasemonkey to add my notes, but it isn't very attractive when I have to write code to do it. A scribble extension would make this dead easy: right click, choose "add scribble", enter whatever text you wanted to and you're done.

Why is this useful? Well, sometimes when you are reading something you may have some interesting thoughts developing in addition to but because of what you're reading. You could open a text editor and make a note of such thoughts, but it might be even better if you could add that note right there into the page you're viewing by the sentence which inspired the scribble (or is relevant to it).

Scribbles would be saved in a database in which each page has an entry with scribbles called from it for displaying on that page whenever you open it. Also, scribbles would be easily saved in a folder so that you don't lose them when moving from one OS to another, for example. It could also employ some sort of an export mechanism allowing you to, for example, export to html or PDF a list of sites you scribbled on with the content of your scribbles.

Anyway, what do you think? Is there a such extension already?

Thanks