function random_imglink(){
  var myimages=new Array()
  //specify random images below. You can have as many as you wish
  myimages[1]="e-banner/Casebook.gif"
 myimages[2]="e-banner/Protein.gif"
  myimages[3]="e-banner/ICDDT(468x60).gif"
  //myimages[3]="e-banner/Casebook.gif"

  //specify corresponding links below
  var imagelinks=new Array()
  imagelinks[1]="http://bentham.org/ebooks/9781608050284/index.htm"
 imagelinks[2]="http://bentham.org/ebooks/9781608050130/index.htm"
  imagelinks[3]="http://www.icddt.com"
  //imagelinks[3]="http://www.java-scripts.net"

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

  if (ry==0)
     ry=1
     document.write('<a href='+'"'+imagelinks[ry]+'"'+' onclick="window.open(this.href); return false;"><img src="'+myimages[ry]+'" border=0></a>')
}

  random_imglink()