a = 2 //最大随机数（图片总数）
var pp = Math.random();
var foot = Math.round(pp * (a-1))+1;
function create() {
this.src = ''
this.alt = ''
}
b = new Array()
for(var i=1; i<=a; i++) { b[i] = new create() }
b[1].src    = "/templets/images/banner1.jpg"
b[1].alt    = "精品素材,一起分享"
b[2].src    = "/templets/images/banner2.jpg"
b[2].alt    = "他山之石,可以攻玉"
var pic = "";
pic += '<img src='+b[foot].src+' border="0"'+' alt='+b[foot].alt+'>';
document.write(pic)