function initRollovers() {
    if (!document.getElementById) return;

    var aPreLoad = new Array();
    var sTempSrc;
    var aImages = document.getElementsByTagName('img');

    for (var i = 0; i < aImages.length; i++) {
        if (aImages[i].className == 'imgOver') {
            var src = aImages[i].getAttribute('src');
            var ftype = src.substring(src.lastIndexOf('.'), src.length);
      var root = src.substring(0, src.lastIndexOf("/") + 1);
      var imgname = src.substring(src.lastIndexOf("/") + 1, src.length);
            var hsrc = root + 'over-' + imgname;

            aImages[i].setAttribute('hsrc', hsrc);

            aPreLoad[i] = new Image();
            aPreLoad[i].src = hsrc;

            aImages[i].onmouseover = function() {
                sTempSrc = this.getAttribute('src');
                this.setAttribute('src', this.getAttribute('hsrc'));
        this.setAttribute('origsrc', sTempSrc);
            }

            aImages[i].onmouseout = function() {
                this.setAttribute('src', this.getAttribute('origsrc'));
            }
        }
    }
}

addLoadEvent(initRollovers);