var BROWSER_UNKNOWN = -1;
var BROWSER_FIREFOX = 0;
var BROWSER_MSIE    = 1;
var BROWSER_SAFARI  = 2;
var BROWSER_OPERA   = 3;

function browser_detect() {
  if (navigator.userAgent.indexOf("Firefox")!=-1) {
    return BROWSER_FIREFOX;
  } else if (navigator.userAgent.indexOf("MSIE")!=-1) {
    return BROWSER_MSIE;
  } else if (navigator.userAgent.indexOf("Safari")!=-1) {
    return BROWSER_SAFARI;
  } else if (navigator.userAgent.indexOf("Opera")!=-1) {
    return BROWSER_OPERA;
  } else {
    return BROWSER_UNKNOWN;
  }
}

function getViewportSize() {
  var viewportwidth;
  var viewportheight;
  
  // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
  if (typeof window.innerWidth != 'undefined') {
    viewportwidth = window.innerWidth,
    viewportheight = window.innerHeight
  }
  
  // IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
  else if (typeof document.documentElement != 'undefined' 
            && typeof document.documentElement.clientWidth !='undefined' 
            && document.documentElement.clientWidth != 0) {
    viewportwidth = document.documentElement.clientWidth,
    viewportheight = document.documentElement.clientHeight
  }
  
  // older versions of IE
  else {
    viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
    viewportheight = document.getElementsByTagName('body')[0].clientHeight
  }
  
  return new Array(viewportwidth, viewportheight);
}