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The Robots.txt protocol, also called the “robots exclusion standard” is designed to lock out web spiders from accessing part of a website. It is a security or privacy measure, the equivalent of hanging a “Keep Out” sign on your door.
This protocol is used by web site administrators when there are sections or files that they would rather not be accessed by the rest of the world. This could include employee lists, or files that they are circulating internally. For example, the White House website uses robots.txt to block any inquiries on speeches by the Vice President, a photo essay of the First Lady, and profiles of the 911 victims.
How does the protocol work? It lists the files that shouldn’t be scanned, and places it in the top-level directory of the website. The robots.txt protocol was created by consensus in June 1994 by members of the robots mailing list (email@example.com). There is no official standards body or RFC for the protocol, so it’s difficult to legislate or mandate that the protocol be followed. In fact, the file is treated as strictly advisory, and does not have absolute guarantee that those contents won’t be read.
In effect, robot.txt requires cooperation by the web spider and even the reader, since anything that is uploaded into the internet becomes publicly available. You aren’t locking them out of those pages, you are just making it harder for them to get in. But it takes very little for them to ignore these instructions. Computer hackers can also easily penetrate the files and retrieve information. So the rule of thumb is—if it’s that sensitive, it shouldn’t be on your website to begin with.
Care, however, should be taken to ensure that the Robots.txt protocol doesn’t block the website robots from other areas of the website. This will dramatically affect your search engine ranking, as the crawlers rely on the robots to count the keywords, review metatags, titles and crossheads, and even register the hyperlinks.
One misplaced hyphen or dash can have catastrophic effects. For example, the robots.txt patterns are matched by simple substring comparisons, so care should be taken to make sure that patterns matching directories have the final '/' character appended: otherwise all files with names starting with that substring will match, rather than just those in the directory intended.
To avoid these problems, consider submitting your site to a search engine spider simulator, also called search engine robot simulator. These simulators—which can be bought or downloaded from the internet— use the same processes and strategies of different search engines and give you a “dry run” of how they will read your site. They will tell you which pages are skipped, which links are ignored, and which errors are encountered. Since the simulators will also reenact how the bots will follow your hyperlinks, you’ll see if your robot.txt protocol is interfering with the search engine’s ability to read through all the necessary pages.
It’s also important to review your robot.txt files, which will enable you to spot any problems and correct them before you submit them to real search engines.
About the Author: XML-Sitemaps.com provides free online tools for webmasters including a search engine spider simulator and a Google sitemaps XML validator.