Creating Accessible Web Pages
This is an enormous topic and considerable training is needed to create truly accessible web pages. The consensus on what makes web pages accessible changes frequently and many people whose full-time job involves designing web pages find it difficult to keep up-to-date.
For this reason many organisations use a Content Management System (CMS) which removes many elements of accessibility from the concern of the generalist User, but doesn't cover the actual content. For example, information for the general public should be able to be understood by the majority of the population regardless of ethnicity or disability.
Even if a CMS is used to produce web pages there is still a need for the creator to have a basic understanding of web accessibility in order that they always incorporate the "basics" such as when or when not to include alternate text for images.
There are many things to consider when creating accessible web pages and the link below will give you more information on this.
The most important thing to remember about forms is that the User should be able to [tab] through the form in the correct order of navigation.
A brief tutorial on producing accessible forms is available from Webaim