var scrollSpeed = 85; 
var step = 1; 				
var current = 0;			
var imageWidth = 800;		
var headerWidth = 800;
var restartPosition = -(imageWidth - headerWidth);
			
function scrollBg(){
	current += step;
	if (current == restartPosition){
		current = 0;
	}
	$('body').css("background-position",""+current+"px 0");	
}
var init = setInterval("scrollBg()", scrollSpeed);