function checkAvailableWidth(){
	var mainnav = $("mainnav");
	mainnav.style.width = (document.body.clientWidth < 1000)? "1000px" : "100%";
	var headernav = $("headernav");
	headernav.style.width = (document.body.clientWidth < 1000)? "1000px" : "100%";
}