// define browser
var nn4 = (document.layers) || (navigator.userAgent.indexOf('Netscape') >= 0)? true : false;
var opera = (navigator.userAgent.indexOf('Opera') >= 0)? true : false;
var moz = (navigator.userAgent.indexOf('Gecko') >= 0)? true : false;
var dom = (document.getElementById && !opera)? true : false;
var ie4 = (document.all && !dom)? true : false;