event.offsetX in Firefox

Answer 1

Unfortunately offsetX and layerX are not exactly the same as offsetX is the offset within the current element but layerX is the offset from the page. Below is a fix I am currently using for this:

function fixEvent(e) {
    if (! e.hasOwnProperty('offsetX')) {
        var curleft = curtop = 0;
        if (e.offsetParent) {
           var obj=e;
           do {
              curleft += obj.offsetLeft;
              curtop += obj.offsetTop;
           } while (obj = obj.offsetParent);
        }
        e.offsetX=e.layerX-curleft;
        e.offsetY=e.layerY-curtop;
    }
    return e;
}