To conditionally show a Twitter Bootstrap styled DIV with a list of error messages, use the rendered property on panelGroup to check whether messageList has messages to be displayed, and if so, render the enclosed content.
layout=”block” displays the output as a DIV, and row is one of the Bootstrap classes for row display.
<div class="span12 alert alert-danger"></div>
Set messages to display from your Backing Bean with:
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("your message");