function appear(place)
{
   document.getElementById(place).style.visibility='visible';
}

function nav(place)
{
	var text;

	if(document.getElementById(place).innerHTML != '') document.getElementById(place).innerHTML = '';
	else 
	{
		switch(place)
		{
			case "current":
			break;   

			default:
	  			alert("An error has occurred.");
		}
	document.getElementById(place).innerHTML = text;
	} 
}