// Initialize and render the menu bar when it is available in the DOM

YAHOO.util.Event.onContentReady("main_navigation", function () {

    // Instantiate and render the menu bar

    var oMenuBar = new YAHOO.widget.MenuBar("main_navigation", { autosubmenudisplay: true, hidedelay: 750, lazyload: true });

    /*
         Call the "render" method with no arguments since the markup for 
         this menu already exists in the DOM.
    */

    oMenuBar.render();

});