I have a feeling what I am about to will not be possible, because well... Apple.
I am making a full-screen web based game, and I have a 8-directional virtual joystick on screen (a circle divided into 8 slices), and as I am playing my game (device rotated in landscape mode), and sliding my thumb around this circle, having a great time playing my game.. And then... Suddenly, the page slides down, a scroll bar appears, and the url bar slides into view on the top of the screen.
I continue trying to play, the next thing I know, notifications slide down covering up half of my screen.
And then I let out a huge sigh, and think to myself (for the 100th time, for the 100th different reason): maybe making a browser based game was a really, really bad idea.