var isNav4, isIE4, isMac, isGecko, is98ME, isForceClick;

if (navigator.appVersion.charAt(0) >= "4") 
{
  if (navigator.appName == "Netscape") 
    isNav4 = true;
  else 
    isIE4 = true;
}

isMac = (navigator.userAgent.indexOf("mac")!=-1)  || (navigator.userAgent.indexOf("Mac")!=-1);
isOSX = (navigator.userAgent.indexOf("OS X")!=-1);
isGecko = (navigator.userAgent.toLowerCase().indexOf("gecko") != -1);
is98ME = (navigator.userAgent.indexOf("Win98")!=-1 || navigator.userAgent.indexOf("Windows 98")!=-1 || navigator.userAgent.indexOf("WinME")!=-1 || navigator.userAgent.indexOf("Windows ME")!=-1)
isVista = (navigator.userAgent.indexOf("Windows NT 6.0")!=-1);

isForceClick = String(location).indexOf("force")>=0;