Doorway pages are web pages that have been created for the sole purpose of ranking highly in the search results for one or two searchterms, and are not normally an integral part of the website. If search engines didn't exist, neither would doorway pages. Some search engine optimizers complain that doorway pages clutter up the search results and, therefore, devalue them for surfers. That view is not without a factual basis, but only in the past. It used to be true that a site could dominate the top results with doorway pages, but that was a failing of the search engines. It used to be possible for site to have 5 or more doorway pages in the top 10 results, and sometimes it was much worse. For instance, when localized Altavistas first appeared, some sites' doorway pages would occupy the top 30, 50 and even more results.

Altavista cleaned up their act and good search engines don't display more than two pages from the same site in the search results for a given searchterm. So doorway pages from a single site cannot clutter up the results. They can fill the top rankings, of course, but not all from the same site. Some people claim that this is cluttering up and devaluing the results for surfers by reducing the relevancy of the results, but they really aren't thinking straight. What difference does it make if a site's doorway page or content page occupies a top ranking? None. A relevant page from the site is listed; that's all. It doesn't devalue the results in any way.

In case of emergency
If you're compelled to use doorway pages, never create more of them than there are "real" pages on your web site. Search engines understand that some pages can't be indexed and will generally allow you to create one page pointing to each page on your site. As long as your doorway pages present unique and useful information, search engines won't ban them.