<zk>
<!--    no flicker without onClientInfo-->
<!--    <div>-->
    <div onClientInfo="">
<!--    add a delay to make it more obvious-->
<!--    <div onClientInfo="Thread.sleep(1000);">-->
        <listbox width="200px">
            <listhead>
                <listheader hflex="7"/>
                <listheader hflex="5"/>
            </listhead>
            <listitem>
                <listcell label="col1"/>
                <listcell label="col2"/>
            </listitem>
        </listbox>
    </div>
</zk>

	<style>
		.z-listbox.hidden-header .z-listbox-header {
			visibility: hidden;
			height: 0px;
		}
	</style>
       ...
        <listbox width="200px" sclass="hidden-header">