A sitemap is an XML file that lists URLs for a site, along with additional information about each URL. Sitemaps give Google and other search engines important information about your website, including:

• A complete list of all URLs on your site, including URLs that may not be discoverable by Google's normal crawling process (for example, non-text pages or URLs containing several parameters.)

• How often the pages on your site change. For example, you might update your product page daily, but update your About Me page only once every few months.

• The date each page was last modified.

• The relative importance of pages on your site. For example, your home page might have a relative importance of 1.0, category pages have an importance of 0.8, and individual blog entries or product pages have an importance of 0.5. This priority ranking only indicates the importance of a particular URL relative to other URLs on your site, and doesn't impact the ranking of your pages in search results

Sitemaps are particularly helpful if:

• Your site has dynamic content.

• Your site has pages that aren't easily discovered by Googlebot during the crawl process - for example, pages featuring rich AJAX or Flash.

• Your site is new and has few links to it.

• Your site has a large archive of content pages that are not well linked to each other, or are not linked at all.

 

While sitemaps can make for speedier crawling and indexing of your pages, there are many other factors that influence the crawling/indexing processes. These other factors include:

• How many sites link to you

• Whether your content is unique and relevant

• Our ability to crawl the pages successfully

• Everything outlined in our webmaster guidelines.

A sitemap provides an additional view into your site (just as your home page and HTML site map do), but sitemaps do not replace our normal methods of crawling the web. Google still searches and indexes your sites in the normal way, whether or not you use this program, and sites are never penalized for using this service. We can't make any predictions or guarantees about when or if your URLs will be crawled or added to our index but over time, as we refine our processes and better understand webmasters' needs, we expect both coverage and time-to-index to improve.

Google adheres to Sitemap Protocol 0.9 as defined by sitemaps.org. Sitemaps created for Google using Sitemap Protocol 0.9 are therefore compatible with other search engines that adopt the standards of sitemaps.org.

Following these guidelines will help Google find, index, and rank your site. Even if you choose not to implement any of these suggestions, we strongly encourage you to pay very close attention to the "Quality Guidelines," which outline some of the illicit practices that may lead to a site being removed entirely from the Google index or otherwise penalized. If a site has been penalized, it may no longer show up in results on Google.com or on any of Google's partner sites.

• Design, content, and technical guidelines

• Quality guidelines

When your site is ready:

• Have other relevant sites link to yours.

• Submit it to Google at http://www.google.com/addurl.html.

• Submit a Sitemap as part of our Google webmaster tools. Google uses your Sitemap to learn about the structure of your site and to increase our coverage of your webpages.

• Make sure all the sites that should know about your pages are aware your site is online.

• Submit your site to relevant directories such as the Open Directory Project and Yahoo!, as well as to other industry-specific expert sites.

Design and content guidelines

• Make a site with a clear hierarchy and text links. Every page should be reachable from at least one static text link.

• Offer a site map to your users with links that point to the important parts of your site. If the site map is larger than 100 or so links, you may want to break the site map into separate pages.

• Create a useful, information-rich site, and write pages that clearly and accurately describe your content.

• Think about the words users would type to find your pages, and make sure that your site actually includes those words within it.

• Try to use text instead of images to display important names, content, or links. The Google crawler doesn't recognize text contained in images.

• Make sure that your TITLE tags and ALT attributes are descriptive and accurate.

• Check for broken links and correct HTML.

• If you decide to use dynamic pages (i.e., the URL contains a "?" character), be aware that not every search engine spider crawls dynamic pages as well as static pages. It helps to keep the parameters short and the number of them few.

• Keep the links on a given page to a reasonable number (fewer than 100).

Technical guidelines

• Use a text browser such as Lynx to examine your site, because most search engine spiders see your site much as Lynx would. If fancy features such as JavaScript, cookies, session IDs, frames, DHTML, or Flash keep you from seeing all of your site in a text browser, then search engine spiders may have trouble crawling your site.

• Allow search bots to crawl your sites without session IDs or arguments that track their path through the site. These techniques are useful for tracking individual user behavior, but the access pattern of bots is entirely different. Using these techniques may result in incomplete indexing of your site, as bots may not be able to eliminate URLs that look different but actually point to the same page.

• Make sure your web server supports the If-Modified-Since HTTP header. This feature allows your web server to tell Google whether your content has changed since we last crawled your site. Supporting this feature saves you bandwidth and overhead.

• Make use of the robots.txt file on your web server. This file tells crawlers which directories can or cannot be crawled. Make sure it's current for your site so that you don't accidentally block the Googlebot crawler. Visit http://www.robotstxt.org/wc/faq.html to learn how to instruct robots when they visit your site. You can test your robots.txt file to make sure you're using it correctly with the robots.txt analysis tool available in Google webmaster tools.

• If your company buys a content management system, make sure that the system can export your content so that search engine spiders can crawl your site.

• Use robots.txt to prevent crawling of search results pages or other auto-generated pages that don't add much value for users coming from search engines.

Quality guidelines

These quality guidelines cover the most common forms of deceptive or manipulative behavior, but Google may respond negatively to other misleading practices not listed here (e.g. tricking users by registering misspellings of well-known websites). It's not safe to assume that just because a specific deceptive technique isn't included on this page, Google approves of it. Webmasters who spend their energies upholding the spirit of the basic principles will provide a much better user experience and subsequently enjoy better ranking than those who spend their time looking for loopholes they can exploit.

If you believe that another site is abusing Google's quality guidelines, please report that site at https://www.google.com/webmasters/tools/spamreport. Google prefers developing scalable and automated solutions to problems, so we attempt to minimize hand-to-hand spam fighting. The spam reports we receive are used to create scalable algorithms that recognize and block future spam attempts.

Quality guidelines - basic principles

• Make pages for users, not for search engines. Don't deceive your users or present different content to search engines than you display to users, which is commonly referred to as "cloaking."

• Avoid tricks intended to improve search engine rankings. A good rule of thumb is whether you'd feel comfortable explaining what you've done to a website that competes with you. Another useful test is to ask, "Does this help my users? Would I do this if search engines didn't exist?"

• Don't participate in link schemes designed to increase your site's ranking or PageRank. In particular, avoid links to web spammers or "bad neighborhoods" on the web, as your own ranking may be affected adversely by those links.

• Don't use unauthorized computer programs to submit pages, check rankings, etc. Such programs consume computing resources and violate our Terms of Service. Google does not recommend the use of products such as WebPosition Gold™ that send automatic or programmatic queries to Google.

Quality guidelines - specific guidelines

• Avoid hidden text or hidden links.

• Don't use cloaking or sneaky redirects.

• Don't send automated queries to Google.

• Don't load pages with irrelevant keywords.

• Don't create multiple pages, subdomains, or domains with substantially duplicate content.

• Don't create pages that install viruses, trojans, or other badware.

• Avoid "doorway" pages created just for search engines, or other "cookie cutter" approaches such as affiliate programs with little or no original content.

• If your site participates in an affiliate program, make sure that your site adds value. Provide unique and relevant content that gives users a reason to visit your site first.

If you determine that your site doesn't meet these guidelines, you can modify your site so that it does and then submit your site for reconsideration.

 

Courtesy

http://www.google.com/support/webmasters/bin/answer.py?answer=35769