I tried
<c:if ...>
<h:outputText .../>
</c:if>
but it doesn't work (I don't remember if I used jstl 1.1 or jstl 1.2 at that time). So I think I need a4j:if.
use rendered
eg..
<a4j:outputPanel id="messageToLogIn" styleClass="imageBox" layout="block" rendered="#{rdiLoginHandler.loggedIn =='false'}">