From the W3C Guidelines it would appear the optimum sites for accessibility are those with simple blue and purple links with no dynamic menu system which works on all historical browsers.

While in their view this may be the ideal website for accessibility, few people require sites of this kind so it becomes a balance between a well designed site and one which is accessible.

If a site is well planned and well coded the accessibility issues will be reduced. So by putting alt tags on images (or longdesc for those with longer content), being able to change the size of the text on the page, ensuring the content is readable without having links that read "more" or "click here" etc., it will be accessible. These are just a few and there are obviously many other accessibility issues to be thought about.

If a user does not have a plug-in it is surprising how many sites do not have an alterative content as many users do not have plug-ins enabled due to company firewalls.

Although there are numerous different types of screen readers depending on the individuals impairment, it is always reommended to try the site in these browsers to see how easy (or difficult) the site is to use.