This webpage hijacks the keyboard in a very nasty way, disabling not only scrolling, but also a bunch of other functions.
What browser are you using?
Before hitting the emulator (and/or editor, not sure) all keys work fine. After, well, only scroll on the mouse worked for moving through the page.
It's fine when I initially open the page, but once I click 'run' I can no longer use PgUp, PgDn, F12, etc.
I'm guessing the emulator captures some input. But even when clicking on other parts of the page, it doesn't 'uncapture'.
FWIW, it doesn't really bother me.