function random_imglink(){
  var myimages=new Array();
  //specify random images below. You can have as many as you wish
  myimages[1]="<img src='/images/banner1.jpg' alt='Head Teacher Update' class='topBanner' />";
  myimages[2]="<img src='/images/banner2.jpg' alt='Head Teacher Update Banner' class='topBanner' />";

var ry=Math.floor(Math.random()*myimages.length);

  if (ry==0)
     ry=1
     document.write(myimages[ry]);
}
random_imglink()