Page Cloaking - To Cloak or Not to Cloak.
By Sumantra  Roy

Page cloaking can broadly be defined as a  technique used to deliver different web pages under different circumstances.  There are two primary reasons that people use page cloaking:

i) It allows them to create a separate optimized page for each search engine and another page which is aesthetically  pleasing and designed for their human visitors. When a search engine spider visits a site, the page which has been optimized for that search engine is  delivered to it. When a human visits a site, the page which was designed for the  human visitors is shown. The primary benefit of doing this is that the human  visitors don't need to be shown the pages which have been optimized for the search engines, because the pages which are meant for the search engines may not be aesthetically pleasing, and may contain an over-repetition of keywords.

ii) It allows them to hide the source code  of the optimized pages that they have created, and hence prevents their competitors from being able to copy the source code.

Page cloaking is implemented by using some specialized cloaking scripts. A cloaking script is installed on the server,  which detects whether it is a search engine or a human being that is requesting  a page. If a search engine is requesting a page, the cloaking script delivers the page which has been optimized for that search engine. If a human being is  requesting the page, the cloaking script delivers the page which has been designed for humans.

There are two primary ways by which the  cloaking script can detect whether a search engine or a human being is visiting a site:

i) The first and simplest way is by  checking the User-Agent variable. Each time anyone (be it a search engine spider  or a browser being operated by a human) requests a page from a site, it reports an User-Agent name to the site. Generally, if a search engine spider requests a  page, the User-Agent variable contains the name of the search engine. Hence, if the cloaking script detects that the User-Agent variable contains a name of a search engine, it delivers the page which has been optimized for that search engine. If the cloaking script does not detect the name of a search engine in the User-Agent variable, it assumes that the request has been made by a human  being and delivers the page which was designed for human beings.

However, while this is the simplest way to implement a cloaking script, it is also the least safe. It is pretty easy to fake the User -Agent variable, and hence, someone who wants to see the optimized pages that are being delivered to different search engines can easily do  so.

ii) The second and more complicated way is  to use I.P. (Internet Protocol) based cloaking. This involves the use of an I.P.  database which contains a list of the I.P. addresses of all known search engine spiders. When a visitor (a search engine or a human) requests a page, the  cloaking script checks the I.P. address of the visitor. If the I.P. address is  present in the I.P. database, the cloaking script knows that the visitor is a search engine and delivers the page optimized for that search engine. If the I.P. address is not present in the I.P. database, the cloaking script assumes  that a human has requested the page, and delivers the page which is meant for  human visitors.

Although more complicated than User-Agent  based cloaking, I.P. based cloaking is more reliable and safe because it is very  difficult to fake I.P. addresses.

Now that you have an idea of what cloaking is all about and how it is implemented, the question arises as to whether you  should use page cloaking. The one word answer is "NO". The reason is simple: the  search engines don't like it, and will probably ban your site from their index  if they find out that your site uses cloaking. The reason that the search engines don't like page cloaking is that it prevents them from being able to  spider the same page that their visitors are going to see. And if the search  engines are prevented from doing so, they cannot be confident of delivering  relevant results to their users. In the past, many people have created optimized  pages for some highly popular keywords and then used page cloaking to take  people to their real sites which had nothing to do with those keywords. If the  search engines allowed this to happen, they would suffer because their users  would abandon them and go to another search engine which produced more relevant results.

Of course, a question arises as to how a search engine can detect whether or not a site uses page cloaking. There are three ways by which it can do so:

i) If the site uses User-Agent cloaking, the search engines can simply send a spider to a site which does not report the  name of the search engine in the User-Agent variable. If the search engine sees  that the page delivered to this spider is different from the page which is delivered to a spider which reports the name of the search engine in the User-Agent variable, it knows that the site has used page cloaking.

ii) If the site uses I.P. based cloaking, the search engines can send a spider from a different I.P. address than any I.P. address which it has used previously. Since this is a new I.P. address, the I.P. database that is used for cloaking will not contain this address. If the search engine detects that the page delivered to the spider with the new I.P. address is different from the page that is delivered to a spider with a known I.P. address, it knows that the site has used page cloaking.

iii) A human representative from a search  engine may visit a site to see whether it uses cloaking. If she sees that the page which is delivered to her is different from the one being delivered to the  search engine spider, she knows that the site uses cloaking.

Hence, when it comes to page cloaking, my  advice is simple: don't even think about using it.

Article by Sumantra Roy. Sumantra is one of the most respected search engine positioning specialists on the Internet. To have Sumantra's company place your site at the top of the search engines, go to http://www.1stSearchRanking.com/t.cgi?2257 For more advice on how you can take your web site to the top of the search  engines, subscribe to his FREE newsletter by going to http://www.1stSearchRanking.com/t.cgi?2257&newsletter.htm