function swap(){
	var caller = this.id;
	var target = document.getElementById("head_img");
	var name = this.src.split(".");
	var x = name[name.length-2].split("/");	
	var image = x[x.length-1].substring(0,(x[x.length-1].length-6));	
	var ext = name[name.length-1]
	target.src = "images/" + image + "." + ext;
}

function addEvent(elm, evType, fn, useCapture){
	if(elm.addEventListener){
		elm.addEventListener(evType, fn, useCapture);
		return true;
	}else if (elm.attachEvent){
		var r = elm.attachEvent('on' + evType, fn);
		return r;
	}else{elm['on' + evType] = fn;}
}

function findthumb()
{
	var thumb = document.getElementById("head_thumbs").getElementsByTagName("img");
	for (i=0;i<thumb.length;i++){
		thumb[i].onclick = swap;
	}
}

addEvent(window, 'load', findthumb, false);