var resizeWin = function(event) {
	var main = document.getElementById('top_head');
	var viewport = getViewPort();
	var width = viewport.width;
	//var height = viewport.height;	
	var height = '400px';
	main.style.width = (width <= 975 ? "975px" : '100%');
	main.style.height = height;
}

var getViewPort = function() {
	var width, heiht;
	if (self.innerHeight) {
		width = self.innerWidth;
		height = self.innerHeight;
	} else if (document.documentElement && document.documentElement.clientHeight) {
		width = document.documentElement.clientWidth;
		height = document.documentElement.clientHeight;
	} else if (document.body) {
		width = document.body.clientWidth;
		height = document.body.clientHeight;
	}
	return {width: width, height: height};
}

var observe = function(element, event, observer) {
	if (element.addEventListener) {
		element.addEventListener(event, observer, false);
	} else if (element.attachEvent) {
		element.attachEvent('on' + event, observer);
	}
};
observe(window, 'resize', resizeWin);
observe(window, 'load', resizeWin);