var width = 640;
var height = 570;

var posx = (screen.width - width) / 2;
var posy = (screen.height - height) / 2;

function emu(tap, title) {
   window.open('http://www.sinclair.hu/java_emu/emu.php?jateknev=' + escape(title) + '&tapfajlnev=' + tap, 'emu', 'status=1,menubar=0,resizable=0,location=0,titlebar=0,width=' + width + ',height=' + height + ',top=' + posy + ',left=' + posx + "'");
}