Quote:
Originally Posted by saj
Doorway pages might improve a web site’s ranking in the search engines but for short term,  If found out, a search engine may ban that website 
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Indeed......using doorway pages may harm your site as it is a black hat SEO practice and your site could be banned anytime when search engine detect it on your site.
Doorway pages are pages specifically made for search engines. Doorway pages contain many links - often several hundred - that are of little to no use to the visitor, and do not contain valuable content. HTML sitemaps are a valuable resource for your visitors, but ensure that these pages of links are easy for your visitors to navigate. If you have a number of links to include, consider organizing them into categories or into multiple pages. But in doing so, ensure that they are intended for visitors to navigate the sections of your site, and not simply for search engines.
Read more here-
http://www.google.com/support/webmas...n&answer=66355