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

  //specify corresponding links below
  var imagelinks=new Array()
imagelinks[1]="http://benthamscience.com/cag"
imagelinks[2]="http://benthamscience.com/cmi"    
imagelinks[3]="http://benthamscience.com/mirna"

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

  if (ry==0)
     ry=3
     document.write('<a href='+'"'+imagelinks[ry]+'"'+' onclick="window.open(this.href); return false;"><img src="'+myimages[ry]+'" border=0></a>')
}

  random_imglink()