Alternatives to window.scrollMaxY?

Alternative to window.scrollMaxY:

document.documentElement.scrollHeight - document.documentElement.clientHeight

gives same result as window.scrollMaxY with ie7, ie8, ff3.5, Safari 4, Opera 10, Google Chrome 3 under DOCTYPE XHTML 1.0 Transitional.

I've got away with document.body.scrollHeight so that

document.body.scrollHeight = window.pageYOffset + screen height in pixels

at the end of the page (on Android).

two years later...

function getScrollMaxY(){"use strict";
    var innerh = window.innerHeight || ebody.clientHeight, yWithScroll = 0;

    if (window.innerHeight && window.scrollMaxY){
        // Firefox 
        yWithScroll = window.innerHeight + window.scrollMaxY; 
    } else if (document.body.scrollHeight > document.body.offsetHeight){ 
        // all but Explorer Mac 
        yWithScroll = document.body.scrollHeight; 
    } else { 
        // works in Explorer 6 Strict, Mozilla (not FF) and Safari 
        yWithScroll = document.body.offsetHeight; 
    } 
    return yWithScroll-innerh; 
}