Not helped by a required disambiguation:

*"Accessible" in common parlance for a website may equate to easy navigation.

*"Accessibility" in a technical sense (that is very much in play around WMUK) equates to "readability" for those using a screen reader.

The latter is a matter of good practice in use of wikitext, so that the HTML on the pages helps rather than hinders. The former is a mixture of good design and good practice (e.g. portals and categories, respectively - if categorisation of pages is deficient, sheer guesswork may be needed to know whether a topic is covered on a wiki or not). 

I'm all for having some good design in the mix. 

Charles