A doorway page is basically a web page that doesn’t really offer any real content to a search engine visitor, but is a blackhat SEO technique for creating multiple keyword rich pages that are used as a gateway (doorway) to the real sites content (they also act as pages to add keyword rich links to the target site).
A single doorway page will concentrate on a specific search phrase or theme with links to the appropriate content on the real site. Some doorway pages expect the search engine visitor to click a link to the real content and others use a fast Meta refresh to the real content, so automatically redirects to the real page before the search engine visitor realizes they are on a doorway page.
If you are part of the blackhat community this old SEO black hat technique has been dealt with via Google for sometime, it’s a huge risk using this technique.
Hosted Doorway Pages
A doorway page can be on the real sites domain (not a good idea BTW!!) or hosted on another domain (hosted doorway pages). You can find software that will take a set of keywords or content and from it create hundreds or thousands of keyword rich doorway pages (the content is usually nonsense, but the search engines don’t have the ability to remove it automatically) that automatically redirect to the site you choose. All you then have to do is upload it to a site that you don’t care if it is banned or not (less risk than adding the doorway pages to your important web site).
Matt Cutts (a Google employee) at https://www.mattcutts.com/blog/seo-mistakes-hosted-doorway-pages/ SEO Mistakes: Hosted doorway pages says the following-
if someone comes to you and says “I’ll give you $N to rent subdomains, subdirectories, or pages from you. Just link to my doorway pages from your content,” I would recommend to say no as well. It can affect the reputation of your domain if you host doorway pages for someone else and then that other person creates spam on the pages on your domain.
and goes on to say-
I wanted to get it out there so people would understand if we started to take stronger action on this.
Suggesting Google will soon be implementing some new feature of their algorithm that can spot this type of blackhat SEO (or maybe they are hiring more manual reviewers, who knows).
So anyone using doorway pages be very careful. I used manually created doorway pages in the first few months of learning SEO (years ago), but no longer do anything doorway like (I never liked what they looked like to visitors).
If you want some links to important content create some new content to link from, when done correctly this adds value to a site with no risk of a search engine penalty. This does take time however, so unlike nonsense doorway pages it isn’t a quick way to gain new links, but is a much better long term strategy.