window.onload = rolloverInit;


function rolloverInit() {
     for (var i=0; i<document.links.length; i++)
{
        var linkObj = document.links[i];
        if (linkObj.id) {
           var imgObj = document.getElementById(linkObj.id + "_Img");
           if (imgObj) {
              setupRollover(linkObj,imgObj);
           }
        }
     }
}

function setupRollover(thisLink,thisImage) {
     thisLink.imgToChange = thisImage;
     thisLink.onmouseout = rollOut;
     thisLink.onmouseover = rollOver;

     thisLink.outImage = new Image();
     thisLink.outImage.src = thisImage.src;

     thisLink.overImage = new Image();
     thisLink.overImage.src = "buttons/on.jpg";

}

function rollOver() {
     this.imgToChange.src = this.overImage.src;
}

function rollOut() {
     this.imgToChange.src = this.outImage.src;
}