// Vergroot div's hoogte wanneer een andere div hoger is
function changeDiv() {
	
	// Div's hoogte's
	var contentDiv    = document.getElementById('mainContent'); 
	var contentHeight = document.getElementById('mainContent').offsetHeight;
	var browserWindow = document.documentElement; 	
	var menuDiv       = document.getElementById('menu'); 
	
	// Client window
	var clientWindowHeight = browserWindow.clientHeight - 130;
	
	// Grootste hoogte?
	var size = Math.max(clientWindowHeight, contentHeight);
	
	// Set height
	contentDiv.style.height = size+'px';
	menuDiv.style.height = size+'px';
	
}

window.onload = changeDiv;
window.onresize = changeDiv;