window.onload = function(){
/*image roll over*/

var rootNode = document.getElementById("mainMenu");	
var imgTag = rootNode.getElementsByTagName("img");
for(var i=0; i<imgTag.length;i++){
	imgTag[i].onmouseover = function(){
		this.src=this.src.split(".gif")[0]+"_over.gif";
		}
	imgTag[i].onmouseout = function(){
		this.src=this.src.split("_over.gif")[0]+".gif";
		}
	}

}