You need a Sitemap if:

• You have a site with only a few backlinks to it.

Search engines like Google follow links to find sites. If you have a new site, Google may not visit all of the pages on your site because those pages may have very few links to them. Sitemaps allow you to tell the search engines about the pages it may not find due to your site having very few incoming links.

• You have poor internal linking on your site

Since we know that search engine bots follow links, if the main page of your site is indexed and your individual pages aren't linked together well, a Sitemap can help you tell the search engine about pages it may not be able to find on your site due to your pages having a poor link structure between each other. Not having menus and not having links on your main pages and on your article pages can create a poor internal link structure between your pages.

• Your site has a lot of dynamic content

If your site has a lot of dynamic content generated from the database and only a few internal pages, you will likely need a Sitemap to tell Google about your site because the Google robot won't be able to find the “pages” of your site – which, since your site is dynamic, aren't really pages. If you don't understand what I mean, let me explain. Some sites may only contain one main page. When you click on a button on such a site, instead of taking you to a new page, a request for information is sent to the database and data is simply returned on the same page – but to you it looks like an entirely new page.

Here is an example. On my niche site for the Wii, ShopWiiWii.com, I use dynamic information to generate information on the game page. If you click on Wii Games along the left hand side. The main game page just shows all of the games, however, if you click on one of the pictures on the right you will see that the Url has additional information appended to it.

Original Url -

http://www.shopwiiwii.com/Wii-Games/

Dynamic Url -

http://www.shopwiiwii.com/Wii-Games/?game=wii+game+Monster+Jam

There is only one Wii-Games page, however, by using the additional information appended to the url, I can tell the page to retrieve certain information from the database and display that information. The Google bot may not be able to find these dynamic “pages” so I need a Sitemap to tell Google that http://www.shopwiiwii.com/Wii-Games/ and http://www.shopwiiwii.com/Wii-Games/?game=wii+game+Monster+Jam are two different pages. The truth is, however, that it there is only one physical page.

• Your site uses a lot of Flash and AJAX

If your site makes extensive use of Flash or extensive use of AJAX, you are going to need a Sitemap because the bots will have a hard time grabbing all of the links when it visits your site. Sitemaps offer you the ability to tell Google about the urls on your site that it may not find because of the Flash or AJAX embedded in your site.