function highlight_header_unit_div(unit_name){
	var selected_div = document.getElementById('header_' + unit_name + '_div_selected');
	var unselected_div = document.getElementById('header_' + unit_name + '_div_unselected');
	selected_div.style.display = 'block';
	unselected_div.style.display = 'none';
}

function unhighlight_header_unit_div(unit_name){
	var selected_div = document.getElementById('header_' + unit_name + '_div_selected');
	var unselected_div = document.getElementById('header_' + unit_name + '_div_unselected');
	selected_div.style.display = 'none';
	unselected_div.style.display = 'block';
}

function set_header_unit_for_page(unit_name){
	highlight_header_unit_div(unit_name);

	// get parent div, highlight it to indicate that this is the page you're on
	// and override mouse events so that it stays highlighted
	var selected_div = document.getElementById('primary_nav_' + unit_name + '_div');
	
	selected_div.onmouseover=null;
	selected_div.onmouseout=null;
}