You've seen these before. One letter is missing from a sequence of vertical 3-letter words. When the correct letters are added to complete the 3-letter words, a new word(s) will be revealed in the shaded spaces reading left to right, horizontally. The puzzle is considered solved when one can reveal the shaded key-word.
<img src=/S/cheers.gif border=0 alt=cheers width=30 height=16>