function show (id, attribute) {
	var element = document.getElementById(id);
	if ( element != null )
	{
	    if (attribute == 'display') {
    		element.style.display = 'block';
	    } else if (attribute == 'visibility') {
    		element.style.visibility = 'visible';
	    }
	}
}
function hide (id, attribute) {
	var element = document.getElementById(id);
	if ( element != null )
	{
		if (attribute == 'display') {
			element.style.display = 'none';
		} else if (attribute == 'visibility') {
			element.style.visibility = 'hidden';
		}
	}
}