var focused = null;

function ex(id)
{
	if (focused == id)
	{
		document.getElementById(id).style.display = 'none';
		focused = null;
	}
	else
	{
		if (focused != null)
		{
			document.getElementById(focused).style.display = 'none';
		}
		document.getElementById(id).style.display = 'block';
		focused = id;
	}
}