var isNav = (navigator.appName == "Netscape") ? true:false;
function no() {
 var code = isNav ? which:event.button
 if(code == 2 || code == 3) {
  alert("©Kamil Střihavka  2004 - 2009 ... pro REFRESH použijte F5");
 }
}     
document.onmousedown = no;
if(isNav) {document.captureEvents(Event.MOUSEMOVE | Event.MOUSEDOWN);}