var impr=false;

function oeffneSitemap(){
if (f){f.close();}
if (impr){impr.close();}
var x = eval((screen.width - 950) /2); 
var y = eval((screen.height - 350) /2);
impr = window.open('siteservice_sitemap.htm','impressum','width=950,height=350,left='+ x +',top='+ y);

impr.focus();


}