The largest search sites Google, Yahoo, Ask and MSN have announced the adoption of a single standard for storing an XML Sitemap. Webmasters are encouraged to add this line to the robots.txt :
Auto-Discovery saves time: the search robot will now find the sitemap itself on the site, so now you don’t need to manually upload it to each search engine. ')
As explained on the site Sitemaps.org , a single standard should facilitate the process of indexing a site by search engines. Using this XML file, the webmaster directly tells the search engine which pages on the site should be indexed. This way, you can significantly save outgoing traffic, and frequently updated pages are indexed more often.
The unified Sitemap protocol was adopted by the “big three” in November last year, and now they are also joined by the Ask.com search engine. The protocol was originally developed by Google and published under the Creative Commons Attribution-ShareAlike license.