var r_image= new Array(3)
r_image[0]="topimages/tpic001.jpg";
r_image[1]="topimages/tpic002.jpg";
r_image[2]="topimages/tpic003.jpg";
var rand_int= Math.floor(Math.random()*3);
document.write("<img src='"+r_image[rand_int]+"'>");