var imgNum = 12;
var ranNum = Math.random();
var ranNum1 = Math.round( (imgNum-1) * ranNum);
imgList = new Array
for (var i = 0; i < imgNum; i++) {
j = i + 1;
imgList[i] = "/images/2010/topbanners/" + j + ".jpg"
}
var imgName = imgList[ranNum1]