var rand=Math.round(Math.random()*3);
var img=new Array(4);
img[0]="/images/home_push1.jpg";
img[1]="/images/home_push2.jpg";
img[2]="/images/home_push3.jpg";
img[3]="/images/home_push3.jpg";

document.write("<img src=\"" + img[rand] + "\" />");