try {
// create a element so that HTMLAnchorElement is accessible
document.createElement('a');
HTMLElement.prototype.click = function () {
if (typeof this.onclick == 'function') {
if (this.onclick({type: 'click'}) && this.href)
window.open(this.href, this.target? this.target : '_self');
}
else if (this.href)
window.open(this.href, this.target? this.target : '_self');
};
}
catch (e) {
// alert('click method for HTMLAnchorElement couldn\'t be added');
}

try {
// create span element so that HTMLElement is accessible
document.createElement('span');
HTMLElement.prototype.click = function () {
if (typeof this.onclick == 'function')
this.onclick({type: 'click'});
};
}
catch (e) {
// alert('click method for HTMLElement couldn\'t be added');
}

function doClick(linkId, e){
if(e.keyCode != 13){
return;
}
var fireOnThis = document.getElementById(linkId)
if (document.createEvent)
{
var evObj = document.createEvent('MouseEvents')
evObj.initEvent( 'click', true, false )
fireOnThis.dispatchEvent(evObj)
}
else if (document.createEventObject)
{
fireOnThis.fireEvent('onclick')
}
}

<img id="a" src="/a.jpg" onclick="alert('a');"/><div onclick="clickObj('a')">click me</div>
<script language="javascript">
<!--
function clickObj(o){
var o = document.getElementById(o);
if( document.all && typeof( document.all ) == "object" ) //IE
{
o.fireEvent("onclick");
}
else
{
var e = document.createEvent('MouseEvent');
e.initEvent('click',false,false);
o.dispatchEvent(e);
}
}
//-->
</script>