function onSwitchImage( layerName ) {
	var divs = document.getElementsByTagName('div');
	var num = divs.length;
	
	for( i = 0; i < num; i++ ) {
		if( divs[i].id.slice( 0, 5 ) == 'copy_' ) {
			divs[i].style.visibility = 'hidden';
			divs[i].style.display = 'none';	
		}
	}
	
	document.getElementById( layerName ).style.visibility = 'visible';
	document.getElementById( layerName ).style.display = 'block';
}