var mainbody = document.getElementById('mainbody')
var mainbodyheight = mainbody.offsetHeight

var navmenu = document.getElementById('navmenu')
var navmenuheight = navmenu.offsetHeight

if(navmenuheight <= mainbodyheight)
{
		navmenu.style.minHeight = mainbodyheight + 'px';

}

if(navmenuheight >= mainbodyheight)
{
	
	mainbody.style.minHeight = navmenuheight + 'px';
}