var SNIFFER = { 
    agt: navigator.userAgent.toLowerCase(),
    v:   parseInt(navigator.appVersion),
    vf:  parseFloat(navigator.appVersion),
    is:  function(browser) { return this.agt.indexOf(browser) != -1; },

    // browser
    is_nav:     function() { return this.is('mozilla') },
    is_firefox: function() { return this.is('firefox') },
    is_gecko:   function() { return this.is('gecko') },
    is_ie:      function() { return this.is('msie') && !this.is('opera') },
    is_ie6:     function() { return this.is('msie 6.') },
    is_ie7:     function() { return this.is('msie 7.') },
    is_opera:   function() { return this.is('opera') },

    // operating system
    is_win:     function() { return this.is('win') || this.is('16bit'); },
    is_mac:     function() { return this.is('mac'); }
}