//found at http://javascript.about.com/library/blfailimg.htm
function failsafeImg()
{
    var badImg = new Image();
    badImg.src = 'images/ThumbNotFound.jpg'; //url to replaceme image goes here.
    for(var i=0;i<document.images.length;i++)
    {
        var cpyImg = new Image();
        cpyImg.src = document.images[i].src;
        if(!cpyImg.width)
        {
            document.images[i].src = badImg.src;
        }
    }
}