Spoof Chrome & Mozilla from getting my actual screen resolution

How do can i send different info from my original ones? I would like to change the monitor resolution only for the browsers, and if its possible and the fps too.
I don’t want to do the developer tool of browsers, i need to change something at my computer so the browser took that info and show it.
I found this : http://jsfiddle.net/jfriend00/bfAYe/ but i don’t know how to use it.
I want to use this for bookmakers, like : bet365.