var Fenster, i=0;

function NeuFenster(ref)
{ 
if(i!=0){if (Fenster.closed!=true){Fenster.close();}}

Fenster= 
window.open("../bilder/kraeuterkatalog/"+ref+"_gross.jpg","NF", "width=320, height=245 ,dependent=yes");
i=i+1;
}