var arrowImg = new Object();
arrowNorm = new Image(10,7);
arrowNorm.scr = "/img/arrow.gif";

arrowAct = new Image(10,7);
arrowAct.scr = "/img/arrow_act.gif";

function menuOn (imgName){
document.images[imgName].src = arrowAct.scr;
}

function menuOff (imgName){
document.images[imgName].src = arrowNorm.scr;
}