This article is also available in Spanish .
Chat rooms present one of the more difficult web challenges for people with disabilities. Since communication in a chat room tends to be fast-paced, people who type slowly may have difficulty keeping up, and people with cognitive or learning disabilities may have difficulty tracking the multiple simultaneous threads of conversation.
For screen reader users, the accessibility of chat rooms depends in part on how they were developed. Screen readers are able to handle some HTML chat rooms, but most current chat rooms are developed using Java, with little or no attention devoted to the application's accessibility. Even accessible chat rooms, however, can be poor in the area of usability for a screen reader user and can present a confusing, difficult-to-navigate interface, particularly as new content is continually added to the page. WebAim's article Accessibility of Online Chat Programs  includes more specific information on chat technologies.
Courseware packages such as WebCT, Blackboard, and Toolbook typically include chat functionality, which instructors can optionally use as a component of their courses. Courseware vendors have recently made significant improvements in the accessibility of their products, but their chat features have continued to present barriers for screen reader users. To remain abreast of improvements in these products, visit the courseware vendors' accessibility web pages. Links to the accessibility pages of some of the more popular packages are available in the AccessIT Knowledge Base article How do courseware products differ on accessibility? 
Voice chat products are becoming increasingly popular and allow users to chat verbally through their computer's microphone and speakers. Simple Software's Chatterbox  is a popular example of this type of product. However, Chatterbox comes in a voice-only interface, which denies access to users who are deaf, but it also comes in interfaces that combine text and voice.
The text and voice chat features of instant messaging programs like MSN Messenger are generally accessible and are well supported by assistive technologies.
-  available in Spanish
-  Accessibility of Online Chat Programs
-  How do courseware products differ on accessibility?
-  Simple Software's Chatterbox