Doorway pages or, for short, “doorways”, are basically just what the term implies: gateways to the web site proper. (Actually, another common term for doorway pages is “gateway pages” or “gateways”.) Typically, a doorway may consist of a graphic and a welcome message plus a “Click here to enter the site” type of link. More sophisticated doorway pages will also contain a site map. The trick behind doorways lies in their source code: they will normally be optimized for web positioning in their headers, with meta tags containing keywords and page descriptions.
Hallway Pages or “hallways” will typically constitute a list of site contents, each feature being hyperlinked to its appropriate page. While hallway pages will not be hidden to the human visitor by default, their prime focus lies in serving as “spider fodder”: similar to the invisible links mentioned above, they are offering individual hyperlinks for the search engine spiders to crawl.
Hallways will also typically be devoid of graphics content, though more often than not they will be endowed with appropriate meta tags to facilitate search engine indexing.