Search engines crawls the net through spiders. They usually discover the pages from links within the site or from other sites. Sitemap protocol is an URL inclusion protocol which allows webmasters to inform search engines what web pages are available for crawling. It is a xml or txt file hosted on web server which lists the URLs within the site. It helps search engines to crawl the web pages within your site but this does not guarantee that your web pages will be included in search indexes. More, it does not influence the way the pages rank in search engines. This year, Google, MSN, Yahoo and Ask have all agreed to adopt “autodiscovery protocol”: add the sitemap URL in robots.txt file and search engines will all find and spider it. This eliminates the need to submit sitemaps to each search engine separately. If you want to speed up the discovery of your pages you can submit the sitemap through Google/Yahoo webmaster tools. And of course, you can use the tools to check sitemap’s syntax and the submission state.

What software should I use to generate the sitemap files?
It’s depending on preferences . Google Code – Sitemaps Third Party Programs & Websites lists a lot of software used for sitemap generating. Some of them needs additional software installed on web server, some of them are free. I like to use Create your Google Sitemap Online – XML Sitemaps for small sites (<500 pages).

Do I have to regenerate the sitemap if I change the content of the site but I do not change the site’s structure?
No, the sitemap file does not need to be regenerated if you do not change the structure of the site. You can resubmit the sitemap if you want.

Does the sitemap.php or sitemap.html file cause any interruption with Google finding the sitemap.xml file?
No, of course not. We recommend creating a sitemap.hml or sitemap.php file too, because it will help your visitors to better navigate within your own website.

Will the priority affect the manner in which our pages are listed when called upon by Google?
No, the priority is a value you give to your pages relative to other pages from your site. It can have values from 0 to 1. The priority you assign to a page will not influence the position your page appears in a search engine’s results page.