var nrgen = 0;
var nrpoza = 0;

poze = new Array;
poze[1] = new Image();
poze[1].src = "http://www.motorworksautorepair.com/Portals/0/Skins/skin_TMWHome/banner1.jpg";
poze[2] = new Image();
poze[2].src = "http://www.motorworksautorepair.com/Portals/0/Skins/skin_TMWHome/banner2.jpg";
poze[3] = new Image();
poze[3].src = "http://www.motorworksautorepair.com/Portals/0/Skins/skin_TMWHome/banner1.jpg";
poze[4] = new Image();
poze[4].src = "http://www.motorworksautorepair.com/Portals/0/Skins/skin_TMWHome/banner2.jpg";

function swapPic() {
var picnr = poze.length - 1;
do {
var nraleator = Math.random();
nrgen = Math.round((picnr - 1) * nraleator) + 1;
} while (nrgen == nrpoza);
nrpoza = nrgen;
document.getElementById('banner').style.backgroundImage = "url("+poze[nrpoza].src+")";
}