Source Code Edit
READ INSTRUCTIONS ARE HERE:
You need an opera browser. Right click (ctrl + click) in a random empty area and press Source. For a shortcut press ⌘U . Change what you want to change and press apply Changes. On the video I advise you to press Full Screen
How to view and edit a source code on any website and save it on your own computer using a macintosh with the opera browser. You right click the empty space and click source code and then the code pops up. A short cut is command button U.