To edit a website:
Go to a website E.G;
http://www.google.co.uk/ then, when on the website click on the address bar and type in: javascript: document.body.contentEditable = 'true'; document.designMode = 'on'; void 0
then press enter.
Once this is done you will be able to do anything you want to it.
The only bad side to this is that it is not permenant, but it is a great laugh when your at your freinds house and they are on a website.
TO RETURN BACK TO NORMAL.. CLICK F5 OR REFRESH!!