function swapPic()
 {
 if(document.getElementById)
   {
   var thePicture=document.getElementById("header");
   var picPath="/css/images/pic"+rnd(5)+".jpg";
   thePicture.style.background="url("+picPath+")";
   }
 }
 
function rnd(n)
 {
 return Math.floor(Math.random() * n) + 1;
 }