/*
      Netscape browsers:
      Browser userAgent=mozilla/5.0 (windows; u; windows nt 5.1; en-us; rv:1.7) gecko/20040614 firefox/0.8
      Browser appName=netscape

      IE:
      Browser userAgent=mozilla/4.0 (compatible; msie 6.0; windows nt 5.1)
      Browser appName=microsoft internet explorer

      Opera:
      Browser userAgent=mozilla/4.0 (compatible; msie 6.0; windows nt 5.0) opera 7.53 [en]
      Browser appName=microsoft internet explorer
  */

  function isNetscape()
  {
     var agt=navigator.userAgent.toLowerCase();
     var app = navigator.appName.toLowerCase();

     if(app == "netscape" && agt.indexOf("opera")<0)
        return true;
     else
        return false;
  }

  function isIE()
  {
     var agt=navigator.userAgent.toLowerCase();
     var app = navigator.appName.toLowerCase();

     if(app == "microsoft internet explorer" && agt.indexOf("opera")<0)
        return true;
     else
        return false;
  }

  function isOpera()
  {
     var agt=navigator.userAgent.toLowerCase();

     if( agt.indexOf("opera")>-1)
        return true;
     else
        return false;
  }

  function isWindows()
  {
     return isThisOS("win");
  }

  function isLinux()
  {
     return isThisOS("linux");
  }

  function isMac()
  {
     return isThisOS("mac");
  }

  function isThisOS(os)
  {
    var agt=navigator.userAgent.toLowerCase();
    if(agt.indexOf(os) > -1 )
       return true;
    else
       return false;
  }
  
  // this function only works for netscape and opera
  function isJavaInstalled()
  {
     var plugs = navigator.plugins;
     var isJava = false;;
     for(i=0; i<plugs.length; i++)
     {
        if(plugs[i].name.indexOf("Java")>-1)
        {
           isJava = true;
           break;
        }
     }

     return isJava;
  }