function showNavigationLayer2( navigation ) {
	for( $i = 1; $i < 5; $i++ ) {
		document.getElementById('navigation_level_3_' + $i).style.visibility = "hidden";
	}
	for( $i = 1; $i < 7; $i++ ) {
		document.getElementById('navigation_level_2_' + $i).style.visibility = "hidden";
	}
	if( navigation != '' ) document.getElementById(navigation).style.visibility = "visible";
}

function showNavigationLayer3( navigation ) {
	for( $i = 1; $i < 6; $i++ ) {
		document.getElementById('navigation_level_3_' + $i).style.visibility = "hidden";
	}
	if( navigation != '' ) document.getElementById(navigation).style.visibility = "visible";
}