var j=parseInt(Math.random()*4);
  j=(isNaN(j))?0:j;

function writeImage(){
  list = new Array();
  list[list.length]='/Portals/_default/skins/pioneerTech/images/sub_right_pros1.jpg';
  list[list.length]='/Portals/_default/skins/pioneerTech/images/sub_right_pros2.jpg';
  list[list.length]='/Portals/_default/skins/pioneerTech/images/sub_right_pros3.jpg';
  list[list.length]='/Portals/_default/skins/pioneerTech/images/sub_right_pros4.jpg';
     
  document.write("<img src='"+list[j]+"' border='0' alt='Prospective Students' >");
}