A sitemap page is a very good way of giving the search engine robot every opportunity to reach your website pages. Since robots click through the links of your web pages, make sure that at least your most important pages are included in the sitemap. You may even want to include all your pages there, depending on the size of your site. Be sure to add a link to the sitemap page from each page on your site.
WWW Robots (also called wanderers or spiders) are programs that traverse many pages in the World Wide Web by recursively retrieving linked pages. The method used to exclude robots from a server is to create a file on the server which specifies an access policy for robots.This file must be accessible via HTTP on the local URL "/robots.txt".
Meaning of *
If the value is '*', the record describes the default access policy for any robot that has not matched any of the other records. For example, to disallow files in the directory web promotion/list and an individual file secret.html, we use the following code:-
You may find more details at https://support.google.com/webmasters/answer/6062596?hl=en&ref_topic=6061961
Keyword density is the ratio of a keyword or key phrases or searchable phrases to the total number of words on that page. It is one of the most fundamental aspects of successful search engine optimization. The keyword density must be okay to improve search engine ranking potential. The relevant keywords or searchable phrases must be researched before developing the site. This method can significantly increase search engine ranking potential. The Search Term Suggestion Tool (powered by Overture) can be used to research keywords. This information can be used to develop keyword density strategy.