var screenW = screen.width; 
var screenH = screen.height;


if (screenW <= 1023 ){
	//show scrollbar  
	document.getElementsByTagName("html")[0].style.overflow = "scroll";
}   
else {  
	//hide scrollbar
	document.getElementsByTagName("html")[0].style.overflow = "hidden"; 
}  

if (screenH <= 640 ){
	//show scrollbar  
	document.getElementsByTagName("html")[0].style.overflow = "scroll";
}   
else {  
	//hide scrollbar
	document.getElementsByTagName("html")[0].style.overflow = "hidden"; 
}