Also known as a "bridge page" or a "gateway page". A doorway page is a web page full of keyword-rich copy that doesn't deliver any useful information on it other than a link into the site and whose sole purpose is to be fed to the search engines.
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Doorway page is a black hat technique to draw search engine visitors to your website. This is done by inserting too much of keywords or phrases regardless of the correct keyword density or its exact placement in the text body of the page.These are web pages that are created for spamdexing. The main purpose or goal behind doing is to send visitors to a different page (in most of the cases that is not desired by the visitor). Doorway Page is also known as bridge pages, portal pages, jump pages, gateway pages, and entry pages.
Doorway pages are used as one of the very earliest strategies for Search Engine Optimisation. Altough it is a very old strategy it have been recognized as a Black Hat optimization technique for quite some time. According to Google :
"Doorway pages are typically large sets of poor-quality pages where each page is optimized for a specific keyword or phrase. In most of the cases doorway pages are written to rank for a particular phrase and then funnel users to a single destination."
This can be explained taking the following example. Suppose a visitor clicks through to a typical doorway page from a search engine results page. The user will be redirected with a fast Meta refresh command to another page. Redirection may use of JavaScript and server side redirection, this is either through the .htaccess file or from the server configuration file. Some scripting languages such as Perl and PHP are also used by doorway pages to generate dynamic pages.
In doorway pages they usually inter link some specific keyword phrases and though these links, provide a funnel effect which guides traffic (real live visitors and search spiders alike) to the intended target pages on the "real" website itself.
Fortunately Doorway Pages are very easy to spot .This although does make it even more dangerous if you do decide to implement them. If a site is having a large number possibly a very large number of pages typically with large numbers of keywords that link and cross link between each other and the real content pages on the site - then it is not harmful to use Doorway Page strategy.
Sometimes doorway pages help in increasing the page rank of a web site but in fact, they will probably get the sites in trouble at some point in time because, they are illegal and forbidden in all major search engines.
But the question arises is that are gateway and doorway pages really worth all the time, expense and effort? The answer to this is that each and every search engine wants that every content should be well-written, contain good, valuable content that is of help to the Internet search community. In real world major Internet search engines such as Google, Yahoo, Alta-Vista and DMOZ, etc supports Web site that is filled with good and valuable content. Also engine spiders (or crawlers) such as Googlebot, Freshbot and all the others; always look for good, useful content the minute they "step into a site".