function sted( )
	{

		if ( BrowserDetect.browser == 'Opera' && BrowserDetect.version > '9.49' )
		{
			var h	= window.innerHeight;
		} else {
			var h	= document.viewport.getHeight( );
		}
		
		$( 'tab' ).style.marginTop	= ( ( h - 500 ) / 2 ).round( ) + 'px';
	
	}
	
	Event.observe( window, 'resize', sted );
	Event.observe( window, 'dom:loaded', sted );
	Event.observe( window, 'load', sted );