initExtCss = function(){
        // find the body element
        var bd = document.body || document.getElementsByTagName('body')[0];
        if(!bd){ return false; }
        var cls = [' ',
                Ext.isIE ? "ext-ie " + (Ext.isIE6 ? 'ext-ie6' : (Ext.isIE7 ? 'ext-ie7' : 'ext-ie8'))
                : Ext.isGecko ? "ext-gecko " + (Ext.isGecko2 ? 'ext-gecko2' : 'ext-gecko3')
                : Ext.isOpera ? "ext-opera"
                : Ext.isWebKit ? "ext-webkit" : ""];

        if(Ext.isSafari){
            cls.push("ext-safari " + (Ext.isSafari2 ? 'ext-safari2' : (Ext.isSafari3 ? 'ext-safari3' : 'ext-safari4')));
        }else if(Ext.isChrome){
            cls.push("ext-chrome");
        }

        if(Ext.isMac){
            cls.push("ext-mac");
        }
        if(Ext.isLinux){
            cls.push("ext-linux");
        }

        if(Ext.isStrict || Ext.isBorderBox){ // add to the parent to allow for selectors like ".ext-strict .ext-ie"
            var p = bd.parentNode;
            if(p){
                p.className += Ext.isStrict ? ' ext-strict' : ' ext-border-box';
            }
        }
        bd.className += cls.join(' ');
        return true;
    }
Adds a listener to be notified when the document is ready (before onload and before images are loaded). Shorthand of {@link Ext.EventManager#onDocumentReady}.
@param {Function} fn The method the event invokes.
@param {Object} scope (optional) The scope (<code>this</code> reference) in which the handler function executes. Defaults to the browser window.
@param {boolean} options (optional) Options object as passed to {@link Ext.Element#addListener}. It is recommended that the options
<code>{single: true}</code> be used so that the handler is removed on first invocation.
@member Ext
@method onReady