Wikis are Web sites that can be added to or edited by visitors to the site. Reference sites such as Wikipedia (en.wikipedia.org) have grown in importance on the Web, and many are highly ranked by search sites such as Ask, Yahoo!, and Google. Unfortunately, it can be difficult to evaluate the credibility of wiki pages because changes occur quickly and repeatedly, with no guarantee of accuracy or credibility. You might want to use wikis when you are beginning to learn about a topic, but avoid citing them as the “last word” on a topic. In fact, those “last words” might change before you submit your final draft.