Thanks. I tried following? it executs but it gets invoked many time for each page. I think once or so for every included xhtml, since my page has template, headers, footer, menu bars in seperate files. I guess that is normal...

public class NoCachePhaseListener implements PhaseListener {

 public PhaseId getPhaseId() {
 return PhaseId.RENDER_RESPONSE;
 }

 public void afterPhase(PhaseEvent phaseEvent) {
 }

 public void beforePhase(PhaseEvent phaseEvent) {

 FacesContext facesContext = phaseEvent.getFacesContext();
 HttpServletResponse response = (HttpServletResponse)facesContext.getExternalContext().getResponse();

 try{
 response.setHeader("Cache-Control", "no-cache, must-revalidate");
 response.setDateHeader("Expires", 0L);
 response.setHeader("Pragma", "No-cache");
 }catch(NullPointerException npe){
 System.out.println("Null http response, no action on cache-control");
 }

 }
}

<lifecycle>
 <phase-listener>au.edu.tisc.util.NoCachePhaseListener</phase-listener>
</lifecycle>

Thanks Lisa, yes my action was not returning empty string.