<navbar orient="vertical" width="200px">
    <navitem label="Home" iconSclass="z-icon-home" />
    <nav label="Get Started" iconSclass="z-icon-th-list" badgeText="3">
        <navitem label="Step One" />
        <navitem label="Step Two" />
        <navitem label="Step Three" />
    </nav>
    <navitem label="About" iconSclass="z-icon-flag" />
    <navitem label="Contact" iconSclass="z-icon-envelope"/>
</navbar>

org.zkoss.zk.ui.metainfo.DefinitionNotFoundException: file:/C:/target/ball/sidebar.zul:23:41: Component definition not found: navbar in [LanguageDefinition: xul/html]

import org.zkoss.zkmax.zul.Navbar;
import org.zkoss.zkmax.zul.Navitem;