Getting null value for div.offsetParen t in Mozilla.

[Orion]

In my code i am trying to access offsetLeft and offsetTop values for a element which is a div, I use offsetParent property to obtain the same. The code i use is

this.tip.style. left = this.handle.off setParent.offse tLeft + 'px';

After debugging i found the value of "this.handle.of fsetParent" is set to null.

I have problems with Mozilla firefox. The code works absolutly fine with IE

My questions :-

1. When do we get element.offsetP arent value as null.
2. Why do we get element.offsetP arent value as null.
3. What is the difference between parentNode and offsetParent properties, why one should not be used for the other.

[mrhoo]

offsetParent is an IE idiom.
this works in IE and the other browsers:

function whereAt(hoo){        
    var T=0,L=0;    
    while(hoo){
        L+= ( hoo.offsetLeft)? hoo.offsetLeft: 0;
        T+= (hoo.offsetTop)? hoo.offsetTop: 0;
        if(hoo== document.body) break;
        hoo= hoo.parentNode;
    }
    return [L,T];
}