"...discoverability, the quality that every point in the
interface has prompts and actions attached to it from which you can
_learn what to do next_. ... Rule 1 of writing software for nontechnical
users is this: if they have to read documentation to use it _you
designed it wrong_.  The interface of the software should be all the
documentation the user needs."
        -- Eric Raymond
http://www.catb.org/~esr/writings/cups-horror.html