You may feel your Web site's logical layout obviates any need for a search tool, but chances are a first-time visitor won't agree. Even if it's a paragon of elegance and efficiency, too many users have been traumatized by poorly organized Web sites to even try browsing anymore. Users are task-focused and want to find specific information as fast as possible. That means using a search tool. The logic behind a usable search tool is simple.
People search because they have a question that needs an answer.
The search tool's job is to learn the question and provide a clear, concise answer. The first thing you should do is put a simple search tool on every page of your Web site. Half of your visitors will use it right from the home page. Others may bounce around the site before deciding to search. Be sure to put the search button near the top of every page, so those users don't have hunt for it.