Searching through source

[cAs]

Hi,

i'm totally new to developing Mozilla Addons and the first thing i want to
try is searching through the source of the current loaded website.

I got all the layout and the search form, but i just can't find a way to
receive the source of the site?! This is what my programm should do:

User enters term -> Addon receives the source of the current active tab ->
Addon parses through the source -> if something is found display an alert
box.

I tried using javascript: document.all[0].innerhtml but - as i expected - it
doesn't access the tab.

Any help is appreciated!

greetings