function setupRollovers() {
    if (!document.getElementsByTagName)
        return;
    var all_links = document.getElementsByTagName('a');
    for (var i = 0; i < all_links.length; i++) {
        var link = all_links[i];
        if (link.className &&
            (' ' + link.className + ' ').indexOf(' rollover ') != -1)
            {
            if (link.childNodes &&
                link.childNodes.length != 0 &&
                link.childNodes[0].nodeName.toLowerCase() == 'img') {
                link.onmouseover = mouseover;
                link.onmouseout = mouseout;
            }
        }
    }
}

function findTarget(e)
{
    /* Begin the DOM events part, which you */
    /* can ignore for now if it's confusing */
    var target;

    if (window.event && window.event.srcElement)
        target = window.event.srcElement;
    else if (e && e.target)
        target = e.target;
    if (!target)
        return null;

    while (target != document.body &&
        target.nodeName.toLowerCase() != 'a')
    target = target.parentNode;

    if (target.nodeName.toLowerCase() != 'a')
        return null;

    return target;
}

function mouseover(e) {
    var target = findTarget(e);
    if (!target) return;

    // the only child node of the a-tag in target will be an img-tag
    var img_tag = target.childNodes[0];

    // Take the "src", which names an image called "something.ext",
    // Make it point to "something_over.ext"
    // This is done with a regular expression
    img_tag.src = img_tag.src.replace(/(\.[^.]+)$/, '_over$1');
}

function mouseout(e) {
    var target = findTarget(e);
    if (!target) return;

    // the only child node of the a-tag in target will be an img-tag
    var img_tag = target.childNodes[0];

    // Take the "src", which names an image as "something_over.ext",
    // Make it point to "something.ext"
    // This is done with a regular expression
    img_tag.src = img_tag.src.replace(/_over(\.[^.]+)$/, '$1');
}

// When the page loads, set up the rollovers
window.onload = setupRollovers;