The sitemap contains information such as the date a particular URL is updated (last modified), how important a particular link is with respect to others (priority), and how often the content in a link changes (change frequency). With this information, the crawling process becomes much easier for the search engines. For example, the information ‘last modified’ allows search engine crawlers to avoid recrawling a document that has not changed its content. Similarly, the priority of a particular URL is given a value between 0.0 and 1.0, where 0.0 refers to the lowest priority page and 1.0 refers to the highest priority page on a Web site. The default priority of a page is 0.5.
As mentioned before, the sitemap allows the search spiders to index different pages in a Web site more intelligently. All of the popular search engines, including Google, MSN, Yahoo, and Ask use the same sitemap protocol, so having a sitemap would surely yield the best overall results for the Web site. However, expert Web masters say that having an XML sitemap does not guarantee that all of the pages will get indexed, but it will help them, no doubt.
Creating an XML Sitemap
Sitemaps can be created from scratch. If you feel that the process is a bit tedious, you can get the help of a sitemap generator that will let you create the sitemap automatically. After creating the sitemap, you can add various XML tags and attributes in the file.
If you are using a content management system (CMS), there are various plug-ins that ease the sitemap submission process. For example, the Google XML Sitemap Generator plug-in is suitable for a WordPress site. Though it is created for Google, Google XML Sitemap also works well with other search engine. The plug-in is very useful because every time an update is made to the site, the module submits the changes automatically, making the indexing process more efficient. Similarly, there are different plug-ins for popular content management systems like Drupal and Joomla.
For a static Web site, you need to upload the XML file to the root of the domain. Common format used for submitting an XML sitemap is www.sitename/sitemap.xml. After uploading the XML file to the domain, you can further edit the robots.txt file to include the sitemap URL by placing this line anywhere in the robot.txt file: Sitemap: http://www.sitename/sitemap.xml.
Sitemaps are meant to supplement the crawl-based mechanism adopted by search engines; they do not replace it though. Using a sitemap does not guarantee that the Web page is always indexed; however, it certainly increases the chances of getting a Web site optimized for better search results.