function randomInt(low, high) 
 { 
     if (low <= high) {
         return Math.floor( Math.random()*(high - low + 1) ) + low; 
     }
     else {
         return NaN;
     }
 }


function randomOnefrom(list) 
 {
     return list[randomInt(0, list.length-1)]; 
 } 


function bkgd() {
 var pic = randomOnefrom(["graphics/Web1.png", "graphics/Web2.png", "graphics/Web3.png", "graphics/Web4.png"]);
 var thispage = document.getElementById('wrapper'); 
 thispage.style.backgroundImage='url(' + pic + ')';
 thispage.style.backgroundRepeat='no-repeat'       
}