Web Page & Site Design
These are all free. Most of the basic html sites cover design issues as well,
get the basics first.

How to sites:

Chapter 5: Learn to Program HTML in 21 minutes (part of Philip and Alex's Guide to Web Publishing - go here to learn about usability.

Creating Killer Websites

Introduction to Web Design a "three half day [on-line] course" by Selena Sol

Web Developers Virtual Library: Designing Attractive Web Pages

Yale C/AIM Style Manual Guide
-  an awesome resource for the serious web designer.

.Usability: how to make it better

Designing more usable websites - From the Trace Research & Development Center, College of Engineering, University of Wisconsin-Madison. - "a pioneer in the field of technology and disability."

useit.com: Jakob Nielsen's Website

How to make your website work for everyone

Visually impared compatibility checker

Bobby - "Bobby is a free service provided by CAST to help Web page authors identify and repair significant barriers to access by individuals with disabilities."

Colorblind compatibility checkers -

Visicheck - check your pages for color blindness readability

Color dificient vision

Safe colours