y = 0; ad = new Array(y);
ad[y++] = '<A href="/" target="_blank"><img src="/adv/banner_468_1.gif" border="0"></a>'
ad[y++] = '<A href="/" target="_blank"><img src="/adv/banner_468_2.gif" border="0"></a>'
ad[y++] = '<A href="/" target="_blank"><img src="/adv/banner_468_3.gif" border="0"></a>'
ad[y++] = '<A href="/" target="_blank"><img src="/adv/banner_468_3.gif" border="0"></a>'
//Continue if more required
x = Math.floor(Math.random()*(y));
document.write(ad[x]);