function randomNum(max)
   {
   var rNum=NaN
   while (isNaN(rNum))
      {
      rNum=Math.floor(Math.random()*(max))
      }
   return rNum
   }

var pic = new Array()
pic[0]="images/imageschange.gif"
pic[1]="images/imageschange.gif"
pic[2]="images/imageschange.gif"
pic[3]="images/imageschange.gif"

imgTag='<img border="0" src="'
imgTag+=pic[randomNum(pic.length)]
imgTag+='" name="b3">'