function dialog_nahled(url, jmeno, w, h) {
	var wf = "";	
  var winl = (screen.width - w) / 2;
  var wint = (screen.height - h) / 2;
  
	wf = wf + "width=" + w;
	wf = wf + ",height=" + h;
	wf = wf + ",top=" + wint;
	wf = wf + ",left=" + winl;
  wf = wf + ",resizable=" + "no";
	wf = wf + ",scrollbars=" + "no";
	wf = wf + ",menubar=" + "no";
	wf = wf + ",toolbar=" + "no";
	wf = wf + ",directories=" + "no";
	wf = wf + ",location=" + "no";
	wf = wf + ",status=" + "yes";
	wf = wf + ",buttons=" + "no";
	window.open(url,jmeno,wf);
}