Thanks and a hat tip to Kathryn:
Web accessibility for people with cognitive disabilities and learning difficulties is one of the most overlooked subtopics of general web accessibility, despite it affecting the largest numbers. A large part of it is that there are so many conditions to understand in this area (far more than say visual or hearing impairments) and a lack of educational information available for learning about it.
In this article we will cover a few of the problems users with cognitive disabilities may have that can affect their ability to use the Web, as well as the things that developers can do to alleviate these problems and things they should avoid. A lot of what is covered will be well known and common sense to many, but is here for completeness.