function gaestebuch( )
{
 GUB=window.open('http://www.pilots-world.com/gaestebuch/index.html','guestbook',"width=650,height=360,scrollbars=yes");
 breite=(screen.width-650)/2;
 hoehe=(screen.height-360)/2;
 GUB.moveTo(breite,hoehe);
 GUB.focus();
}