function change0 () {
}
 function change1 () {
    document.images['button1'].src = "/images/mainte_hover2.jpg";
}
 function change2 () {
    document.images['button2'].src = "/images/irr_hover.jpg";
}
 function change3 () {
    document.images['button3'].src = "/images/inst_hover.jpg";
}

function disable0 () {
}

function disable1 () {
    document.images['button1'].src = "/images/mainte_normal2.jpg";
}

function disable2 () {
    document.images['button2'].src = "/images/irr_normal.jpg";
}

function disable3 () {
    document.images['button3'].src = "/images/inst_normal.jpg";
}