function matchHeight() {
	var finalHeight = document.getElementById('container').offsetHeight - document.getElementById('header').offsetHeight - document.getElementById('footer').offsetHeight;
	var mainElement = document.getElementById('main');
	mainElement.style.height = finalHeight + 'px';
}	
window.onload = function() {
	matchHeight();
}
window.onresize = function() {
	matchHeight();
}