They are called doorways because they act as an entrance to the site from the search engines. A hallway page links to many doorways for a specific engine. They are mainly used to reduce the number of pages that are submitted to that engine. Notice that you would never use a doorway page for a directory like Yahoo, they are intended only for search engines that use spiders. Why Doorways Are Necessary Doorway pages can solve problems that are created by the design of a website as well as problems that are inherent to search engines and their technology.
Search engines have different algorithms for ranking pages.
Because each engine gives a different weight to the same page elements, it is impossible for one page to rank highly on all search engines. The way to get around this is to create a page optimized for each engine. Doorway pages are often needed because the main web site has pages hostile to the search engine spiders . This includes having frames or dynamically created pages. Another advantage of doorway pages is that they can eliminate the keyword guessing game.