may be it's a dumb reply, but is it the (a) preview pane you are talking about or (b) the actual app deployed on the web server and viewed through browser.
If it (a) then don't worry about it it will be ok when you actually deploy it.
if it's (b) then you must have felt like
after reading the above two line.
In that case I don't have any concrete suggestions coz this never happened to me before. However you could check if your project path includes the jsf implementation jars and that the 'UserBean' has proper entry in <managed-bean> section.