var links = ( screen.availWidth - 700 ) / 2
var oben = ( screen.availHeight - 650 ) / 2

function show(URL)
{
if(document.images)
showWin = open(URL,"foto","width=750,height=540,menubar=no,status=no,locationbar=no,resizable=yes,scrollbars=no");
showWin.moveTo(links,oben);
showWin.focus();
}