JavaScript not working in IE 6/7 for my website

Question

I have some code running on my website which will detect if a div with the id, photo, is showing on the screen or is scrolled onto the screen. If the div is showing, a class is added to the div which will cause a background image to load inside the div. The intent is to lazyload the image so that the site loads faster.

It is working great in all browsers except for IE 6/7. Can someone tell me what is wrong with the below code that prevents it from working in these IE browsers?

function $(a){
    return document.getElementById(a)
}
function scrll(){
    function a(d){
        var f=d.offsetTop,
            e=d.offsetLeft,
            c=d.offsetWidth,
            b=d.offsetHeight;
        while(d.offsetParent){
            d=d.offsetParent;
            f+=d.offsetTop;
            e+=d.offsetLeft
        }
        return(f<(window.pageYOffset+window.innerHeight)
            &&e<(window.pageXOffset+window.innerWidth)
            &&(f+b)>window.pageYOffset&&(e+c)>window.pageXOffset)
    }
    if(a($("photo"))){
        $("imgholder").className="pic11 pic21";
        if(window.removeEventListener){
            window.removeEventListener("scroll",scrll,false)
        }else{
            if(window.detachEvent){
                window.detachEvent("onscroll",scrll)
            }else{
                window.onscroll=null
            }
        }
    }
}
if(window.addEventListener){
    window.addEventListener("scroll",scrll,false);
}else{
    if(window.attachEvent){
        window.attachEvent("onscroll",scrll);
    }else{
        window.onscroll=scrll;
    }
}
setTimeout(scrll,1);

The code is active on my website: http://www.ericperrets.info/

Answer 1

IE doesn't have innerHeight. Use this function instead:

function getWindowHeight()
{
    if (window.innerHeight) return window.innerHeight;
    if (window.document.documentElement.clientHeight) return window.document.documentElement.clientHeight;
    return window.document.body.clientHeight;
}

Also, a good article explaining differences between browsers is at http://www.howtocreate.co.uk/tutorials/javascript/browserwindow