Trick or Treat. Be so sweet. Give me something good to eat! Every day this week we've looked at a different sppoooookkyy aspect of both search engine optimization and web search. I hope you've enjoyed it, and had a fangs-tastic good time (the puns just keep comin', don't they!) Today, in honor of Free Candy Day, we'll show you how to be the scariest monster on the block. If you know the meanings of these words: Boolean , click-through's , and unique visitor , you get a free broom (flying lessons not included).