Robot.txt is a file that the major search engine bots read from your directory. This file has allow and disallow options to tell the bot what pages or folders not to crawl and index. All you have to do is make a blank .txt file in your root folder and name it robots. You can use this http://www.mcanerin.com/EN/search-engine/robots-txt.asp to generate yourself the stuff to put in the robots.txt. You dont have to allow every bot though as they welcome themselfs but its good to disallow the robot from crawling stuff you dont wish it to.
Question: robots.txt ? Answer: The original 1994 Robots Exclusion Protocol description, as currently deployed. Jean-Luc
Definitely Jean-Luc, that site can be considered the authority on robots.txt and where you can find everything about it