function toggleMenuVisibility(id)
{
	var ul = document.getElementById(id).firstChild;
	var span;
	while(ul.nodeName != "UL")
	{
		if(ul.nodeName == "DIV")
		{
			span = ul.firstChild;
		}
		ul = ul.nextSibling;
	}
	if(ul.style.display == "block")
	{
		ul.style.display = "none";
		span.innerHTML = "►";
	}
	else
	{
		ul.style.display = "block";
		span.innerHTML = "▼";
	}
}