If a website has a very appealing graphical layout, it will be probably able to keep the surfers inside the website whenever they will get there. The problem is that spiders can understand only text therefore they may rank badly the website dropping the number of visitors. Restructuring the website to add text and remove some of the design features costs time and money. Cloaking is cheaper but it requires a database with the IP addresses used by the spiders, requiring some kind of regular maintenance. The easiest and fastest solution is to keep the old design and add external pages that are specifically designed to perform well in the search engines. Those are doorway pages.
The concept of doorway page changed a bit in the last years. Since nowadays the inbound links are usually a fundamental element of the ranking algorithm, it is no more possible just creating pages full of keywords, optimising them for spiders and with an auto-redirection to the main site. But you still can use doorways pages in two main methods.
A first elegant way of using doorway pages is creating a dozen of well optimized pages. These doorway pages are supposed to not be seen by users, consequently they can be generously optimised. Every one of the doorway pages has to be linked only to the relevant content page in order to transfer the maximum weight, according the PageRank algorithm. Finally you have to create a hallway page, liked from the relevant content page and linked to all the doorway pages. The relevant page will lose a bit of rank for the outbound link but it will receive a dozen of backlinks from the doorway pages hence it will gain rank instead of losing it. The spider will find the hallway page from the relevant content one. The link to the hallway page has to be hidden so that no human user will follow it, but in this way you can avoid any kind of redirection in the doorway pages. This is a solution that can be easily automated.
The second solution cannot be automated but, on the other hand, it cannot be spotted by a search engine. In this case you will choose a page with relevant content, and you will create a group of pages that have outbound links to that page. Every page is linked to that main content page and it has a link to all the doorway pages. Those pages are optimized for the search terms and every one for a different term. A strategy to create the doorway pages is to split the main page in more pages, to create "further notice" pages, or add some content to a page which presents a larger picture after the user has clicked on the smaller one, included in the main content page. Since the content which is added is natural there is no chance of a penalty, unfortunately this solution requires much more time than the first one.