Sitemap formats
There are many sitemap formats that all have ways to help your site get spidered by various means. 4 different formats for your sitemap spring to mind. Google, HTML, OPML, and Yahoo offer different ways for you to map out your site and get noticed. Sitemap generator services like AutoMapIt.com can create these sitemap files and keep them updated for you to make your life easier.
Google Sitemap uses an XML format to allow you to list the URL, date last modified, how frequently Google should spider your pages, and relative importance to the other pages on your site. The first time you submit a sitemap, you should go to http://www.google.com/webmasters/sitemaps and sign up for an account. Google will decide whether or not they will crawl your site and how much of it they will, but for any quality site, this should direct them to all of your pages
HTML sitemaps tie directly into your site and are viewable by users of your site and Search Engine spiders alike. It is common practice that every page on your site links to the sitemap and that the sitemap links to every page on your site. Every Search engine no matter how simple can access your HTML sitemap and process it’s contents. It is no more than a webpage with links on it as far as spiders are concerned.
OPML sitemap is another XML format that predates the Google sitemap and helps browsers and some SE spiders to navigate your site. You may want to begin your search for OPML info at http://www.opml.org/. There are some good resources to research the exact format for OPML on the web in your favorite search engine so I won’t go into the ugly details here, but OPML is still a useful sitemap to have. There are a few implementations that exist using it and the potential is there for this to be bigger than Google sitemaps… if it wasn’t for the name. One of the benefits of OPML is that it works at the site level… as long as you have access to the pages, you can add an OPML sitemap and all spiders have an equal chance of finding your sitemap without the need for a special submissions process like Google uses.
Yahoo sitemap uses a format that allows you to place all of your links in a plain text file with each new URL on it’s own line. You can submit this file through the Yahoo Search submission page at http://submit.search.yahoo.com/free/request before you go to that page, compile a list of all of your pages with one URL per line and store it on your server as a .txt file. When you go to the Yahoo submission page, enter the URL of your txt file and they will be able to search your list as Google does. This format must be specially made for Yahoo and must be submitted directly through their form on their site. That makes this the least attractive solution, but why pass it up?
All of these sitemap formats have their strengths and weaknesses and all should be utilized for what they have to offer. Using all of the sitemaps available to you is one sure way to open your most hidden pages and ensure that all spiders can find your site and all it has to offer.