function openwindow (adress, pwidth, pheight)
{
	var width = screen . width / 100 * 85 ;
	var height = screen . height / 100 * 70 ;

	if ( pwidth ) width = Math . min ( pwidth, width ) ;
	if ( pheight ) height = Math . min ( pheight, height ) ;
	
	var left = ( screen . width - width ) / 2 ;
	var top = ( screen . height - height ) / 2 ;

	popup_window = window . open ( adress, "Druckansicht", 'scrollbars=yes,width='+width+',height='+height+',resizable=yes,dependent=yes,left='+left+',top='+top+',screenX='+left+',screenY='+top ) ;
	popup_window.focus();
}