var agt=navigator.userAgent.toLowerCase();

var is_ie = (agt.indexOf("msie") != -1);
var is_opera = (agt.indexOf("opera") != -1);
var is_gecko = (agt.indexOf('gecko') != -1);
var is_firefox = (is_gecko && (agt.indexOf('firefox') != -1));
var is_safari = (is_gecko && (agt.indexOf('safari')!=-1));
var navegador = "";
if (is_ie)
  navegador = "ie";
else if (is_opera)
  navegador = "opera";
else if (is_firefox)
  navegador = "firefox";
else if (is_safari)
  navegador = "safari";
else
  navegador = "NA";


// os detection
var is_pc=(navigator.platform.substring(0,3)=='Win');
var is_mac=(navigator.platform.substring(0,3) == 'Mac')

// resolution check
var sw=screen.width;
var sh=screen.height;