FireFile
Firebug was created to detect a problem not to be a debugger. but you can save change if you add new tool that integrate firebug with save changes. it is FireFile, click here
http://thelistoflist.blogspot.com/2010/04/how-to-save-change-you-make-in-firebug.html.
FireFile provide the desired functionality by adding a small PHP file to the server side.