function addLoadEvent(func) 
{
	var oldonload = window.onload;
	if (typeof window.onload != 'function') 
	{
		window.onload = func;
	} 
	else 
	{
		window.onload = function() 
		{
			if (oldonload) 
			{
				oldonload();
			}
			func();
		}
	}
}	

function toggle_visibility(element_id) 
{ 
	div = document.getElementById( element_id ) 
	div.style.display = (div.style.display == 'none') ? 'block' : 'none'; 
}