window.onload = loopImages;

function loopImages()
{
    for(var i=0; i<document.images.length; i++)
    {
        if(document.images[i].mouseover == "true")
        {
            setupRollover(document.images[i]);
        }
    }
}

function setupRollover(thisImage)
{
    thisImage.outImage = new Image();
    thisImage.outImage.src = thisImage.src;
    thisImage.onmouseout = rollOut;
    
    thisImage.overImage = new Image();
    thisImage.overImage.src = "images/" + thisImage.id + "-over.gif";
    thisImage.onmouseover = rollOver;
}

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

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