function rollover(imageName) {
        if (document.images) {
                
                if (imageName.substring(imageName.length-3,imageName.length)!="_on") {
                        document[imageName].src = "images/" + document[imageName].name + "_on.jpg";
                }
        }
}

function rollout(imageName) {
                        if (document.images) {
                                document[imageName].src = "images/" + document[imageName].name + "_off.jpg";
                        }
}