After Jagex changed their website design, the old ad & menubar removers became out-of-date. This fixes it and should work with all Stylish-supported browsers (and you likely have one).

Instructions:
1. Install Stylish, restart browser.
2. Install this style and set your browser to fullscreen mode.
3. Go to Runescape and open settings:
- Set Screen Sizing to RESIZABLE
- Go to Manual Setup -> Custom -> Max Screen Size = ANY

And you're ready to play fullscreen again ;)

I wish someone could donate ma a dollar for coffee :)