window.onload = function() {
    wireMouseOver("videoLink", "video.gif", "video2.gif");
    wireMouseOver("resourcesLink", "resources.gif", "resources2.gif");
    wireMouseOver("contactLink", "contact.gif", "contact2.gif");
};

function wireMouseOver(id, normalFile, overFile) {
    var image = document.getElementById(id);
    image.onmouseover = function() {
        image.src = "img/" + overFile;
    };
    image.onmouseout = function() {
        image.src = "img/" + normalFile;
    };
}