var state = 'hidden';

function showhide(layer_ref)
{
	if (state == 'visible')
	{
		state = 'hidden';
	}
	else
	{
		state = 'visible';
	    document.getElementById('iframe4').src = 'Contacto.html';
	}

	if (document.all)
	{
		eval( "document.all." + layer_ref + ".style.visibility = state");
	}
	if (document.layers)
	{
		document.layers[layer_ref].visibility = state;
	}
	if (document.getElementById && !document.all)
	{
		maxwell_smart = document.getElementById(layer_ref);
		maxwell_smart.style.visibility = state;
	}
}