One of the ways that you can insure that a Search Engine Spider crawls your site deeply is to provide it a road map of your site. This road map, called a "Site Map" is a very simple page that only serves one purpose from a Search Engine Optimisers point of view - to get those interior pages into a Search Engine's index. Failure to make a Site Map is a huge mistake. If all you do is index your first, or home page, the internet won't necessarily see everything you have to offer.
Imagine what use a road atlas would be if it got you only 50 miles into a 300 mile journey, then gave you no further information? A Site map will give the search engine spiders and therefore the internet a complete road map of your website, instead of them only finding their way partly into it.
Before site maps were recognised by the Search Engine Optimisation community as a tool for good search results, they were used by large companies to help visitors to their site find out where a particular service or product was located. For example: If you want to do some sort of business with your bank online, you might find that their home page doesn't quite get you to the exact location on their site that you want. A typical bank might offer Car Loans, Student Loans, Home Loans, Credit Cards, Investment Accounts, etc. And if you arrived at this Banking site on a page other than the home page, you might get a little confused from a site navigation standpoint. So, Site Maps were created.
A Site Map is a page that contains a basic HTML link to EVERY page on that web site. Every Page, not just your main topics. Site Maps do not need to be fancy, they just need to contain a logical order and links to all of your pages.
First, a site map gives your customers an easy navigation system to every page in your web site. Please don't confuse the use of a site map as a replacement for logical navigation on your regular pages. You want to make sure that your site can be navigated simply and easily from any page on your site. However, some people prefer to see the entire site's structure on one page and choose their destination from it. Second, a Site Map is a fantastic way to get a Search Engine Spider to see and crawl and ultimately every single page in your site and a perfect solution for ensuring that a Spider can get to every one of those optimised pages.
Third, and by far the most important thing, a Site Map provides an opportunity to send Link Reputation to a particular page. Link Reputation is perhaps one of the most important factors in Off Page Search Engine Optimisation. You want the links on your Site Map Page to "say" the right thing about the pages that they are linking to. It's like a Vote, so make sure that your Site Map is voting correctly for all of your interior pages. Fourth, Site Maps are also an additional way to distribute Google and Yahoo Page Rank. If your Site Map is just one link off of the first page, it can pass a significant amount of Google Page Rank deep into your web site. This helps create a site structure where just about every internal page has the same chance of ranking well as your home page.
Make sure you design a good Site Map!