var imgOn = new Array();

for( i=0; i <= 6; i++) 
{   imgOn[i] = new Image();
   imgOn[i].src = "images/menun" + (i+1) + ".gif";
  }

var imgOff = new Array();

for( i=0; i <= 6; i++) {
imgOff[i] = new Image();
imgOff[i].src = "images/menu" +  ".gif";
}

function imageOn(n) {
    document.nbar.src = imgOn[n].src;
}

function imageOff(i) {
    document.nbar.src = imgOff[i].src;
}