There's nothing that can be done without native code. So, it's
not possible in the browser, but can be done for Phonegap, Rhodes, etc.
The UIWebView is contained within another native view. The
UIWebView "conveniently" scrolls the UIWebView inside this
native view to bring the focused element into view.
Besides headers, this wrecks havoc with iScroll, etc. You don't
want the UIWebView scrolling itself around - you want to take control
and scroll the iScroll window instead.
It's possible to subclass the outer view with native code, and
block the scrolling. There is a plugin for PhoneGap. And I've done
it for Rhodes.
It's.... complicated.