myLink.onmouseover = showLinkAttr;
function showLinkContent(evt) {
    if (evt) {
        var url = evt.target;
    }
    else {
        evt = window.event;
        var url = evt.srcElement;
    }
..............

myLink.onmouseover = showLinkAttr;
  function showLinkContent(evt) {
        evt = window.event;
        var url = evt.srcElement;

evt = evt || window.event;//evt is equal to itself, if it's not undefined, else it's a reference to the global object

var target = evt.target || evt.srcElement;