var bgPos = 0; 
var scrollDelay = 50;

function Scroller(){
	if (document.getElementById("head")) { 
		document.getElementById("head").style.backgroundPosition  = bgPos + 'px 0px'; 
		bgPos = bgPos + 1; 
		setTimeout("Scroller()", scrollDelay); 
	} 
} 

window.onload = Scroller;