NotificationBar is a fixed positioned panel either at the top or the bottom of the page.
<style>
    .top {
        filter: alpha(opacity=80);
        opacity: 0.8;
        padding: 50px 0 0 50px;
        z-index: 1000;
    }
</style>
<div class="card">
    <p:notificationBar position="top" effect="slide" styleClass="top" widgetVar="bar">
        <h:outputText value="PrimeFaces Rocks!" style="font-size:36px;"/>
    </p:notificationBar>
    <p:commandButton value="Show" onclick="PF('bar').show()" type="button" icon="pi pi-arrow-down"/>
    <p:commandButton value="Hide" onclick="PF('bar').hide()" type="button" icon="pi pi-arrow-up"/>
</div>