This is perfectly understandable because the most relevant sites are always listed first. So if the surfer doesn't find what they want within the first 20 - 30 listings, they'll simply do a new search. Every search engine wants the same thing - Websites that are filled with good, useful content. All search engines base their ranking methods on this criteria. If you'll recall, I advised against using frames, so if you do use frames, you'll have to do your own research.
Search engines use an indexing software agent more commonly referred to as robots or spiders.
They go from URL to URL until they have visited every Web site on the Internet. When a spider crawls a site, it makes a record of the full text of every page within the site. Next, it continues on it's journey to visit all of the external links. This is how search engines are able to find your site regardless of whether or not you register your URL with them. However, URL submissions does speed up the process because it prompts the agent to visit and index your site instead of waiting for it to locate you.