function adjustWidth(){
	var itemWidth = 220;
	var winWidth = window.document.body.clientWidth;
	var main = document.getElementById("main");
	main.style.width = (Math.floor((winWidth-330)/itemWidth) * itemWidth) + "px";
}

if (document.addEventListener) {
	document.addEventListener("DOMContentLoaded", adjustWidth, false);
}

window.onload = adjustWidth;
window.onresize = adjustWidth;