The file that is used to tell robots and crawlers what not to crawl on your site. Robots Exclusion Protocol is a method that allows Web site administrators to indicate to visiting robots parts of your site should not be visited by the robot. When a robot visits a website, first check the robots.txt file in the root directory.
If it can find this file, it will scan the contents to see if it can recover additional documents (files). You can customize the robots.txt file to apply only to specific robots, and deny access to certain folders or files. Here is a sample robots.txt to prevent all robots to visit the entire site: –
# Tells Scanning Robots Where They Are and Are Not Welcome
# User-agent: can also specify by name; “*” is for everyone
# Disallow: if this matches first part of requested path,
# forget it
User-agent: * # applies to all robots
Disallow: / # disallow indexing of all pages
The recording begins with the lines of a user agent or more, stating that robots apply to the records, followed by “Disallow” and “Allow” instructions for the robot. To assess whether access to a URL is allowed, a robot must try to match the roads and let the lines do not allow the URL, in the order they appear in the folder. The first match found is used. If not found, the default assumption is that the URL is allowed.
Spiders and Robots Exclusion
Web Robots are programs that automatically traverse the hypertext structure by retrieving a Web document and recursively retrieving all documents that are referenced. This page explains how you can control what these robots to do while visiting your site.
Targeted Search Engines
Targeted search engines sometimes called topical search engines are the most specific of them all. These search engines are very limited, often on a general topic such as medicine or branches of science, travel, sports, Education etc..
Examples of targeted search engines covered include citysearch, Yahoo Travel and search music, and like other forms of search engine ranking criteria vary from one search engine to another.
In reviewing the specific search engines for SEO, please note that many of these search engines are much more specific than the search engines primary or secondary. Specific search engines for research that is relevant to your subject (as Education, pets, sports, places, and so on).
Search Engine Market Share
Ten years Ago:
In 2010 Search Engine Market