Content management systems (CMS) have become very popular in the last 3 years or so. They usually are pretty easy to install and to upgrade, but not all of them have accessibility in mind. What often happens is that the theme designer has to make it her or his business to create a site as accessible as possible.
I came across some CMS that have accessibility integrated into the system in an article written by the National Center on Disability and Access to Education named NCDAE Tips and Tools: Content Management Systems & Accessibility.
They explain the major challenges that people with disabilities face while using a regular CMS and give us advice on how to choose a responsible system. Most of the systems they recommend have an accessibility page stating there attempt to respect accessibility guidelines. This is valuable information that can help anyone accessing the site. Read this article before considering any CMS.