What I'm trying to do is to save the changes I make to CSS and HTML on different sites with Firebug.
Just to be clear, I don't expect Firebug to upload the changes to the server via FTP or anything. I just want to save the changes locally, so only I will be able to see them.
For example I've seen a few Firefox/Chrome extensions that add a download button under every video on Youtube, so I know it's possible to do that somehow.
If you have a different way to achieve what I'm trying to do, I'll be glad to hear about it.
(It doesn't have to be with Firebug.)
Thanks in advance!
If you don't mind using Web Developer Toolbar it's easy to save changes made to the DOM (and CSS).
When you install the toolbar, you'll get a "View Source" menu, click on that and choose "View generated source". Then just copy and paste that into a .html file.
You did not say if you alter your HTML or CSS, if CSS, FireFile is a very good addon for this.
Edit, with some Googling, i found FireDiff, which states that it can export changes made in Firebug, i have not tested it bit it's worth checking out.