var dom_implementation = document.implementation && true;
var dom_cerate_document = dom_implementation && document.implementation.createDocument;
var dom_feature = dom_implementation && document.implementation.hasFeature;
var moz = dom_cerate_document && dom_feature;
var safari = (navigator.userAgent && navigator.vendor && (navigator.userAgent.toLowerCase().indexOf("applewebkit") != -1 || navigator.vendor.indexOf("Apple") != -1));
var ie = document.all && window.ActiveXObject && navigator.userAgent.toLowerCase().indexOf("msie") > -1  && navigator.userAgent.toLowerCase().indexOf("opera") == -1;
var nn4 = (navigator.appName.indexOf("Netscape") > -1 && navigator.appVersion.indexOf("4") > -1) ? true:false                 
var nn6 = (document.getElementById) ? true:false