window.onload = function() {checkBrokenLinks(); }

function checkBrokenLinks() {
    for (var i = 0; i < document.images.length; i++) {
        if (!IsImageOk(document.images[i])) {
            document.images[i].src="/products/unavailable.jpg";
        }
      }
    }   
function IsImageOk(img) {
    if (!img.complete) {
        return false;
    }
    if (typeof img.naturalWidth != "undefined" && img.naturalWidth == 0) {
        return false;
    }

    return true;
}