function oeffnenewsletter (url)
{
 var xkoordinate=(screen.width-400)/2;
 var ykoordinate=(screen.height-500)/2;
 fenster = window.open(url, "newsletter", "width=450,height=300,status = no,toolbar = no,menubar = no,location = no,resizable = no,titlebar = no,scrollbars = yes,fullscreen = no");
 fenster.moveTo(xkoordinate,ykoordinate);
 fenster.focus();
}