function equalColumns(){
  var l = document.getElementById('mainNav');
  var r = document.getElementById('mainContent');
  var c = document.getElementById('content');
  var f = document.getElementById('footer');

//  if(l.offsetHeight < 600){
//  	l.style.height = 600 + "px";
//  }
  new_height = l.offsetHeight - 230;
  if(c.offsetHeight < 330){
  	//c.style.height = new_height + "px";
	c.style.height = l.offsetHeight + "px";
  }
  r.offsetHeight >= l.offsetHeight ? l.style.height = r.offsetHeight + "px" : r.style.height = l.offsetHeight + "px";
  
  
}
window.onload = function(){
equalColumns();
}