If you’re starting with web design and development, then you must read the following list of free e-books. It includes html, css, ajax, seo etc..
Using XHTML
HTML5 WTF?
Faster, and More Secure Webfonts
Pro Drupal Development
JavaScript Programming for the Absolute Beginner
 The Elements of Typographic Style Applied to the Web
Foundations of Ajax
Search User Interfaces
Web Style Guide: Basic Design Principles for Creating Web Sites
Using Joomla: Building Powerful and Efficient Web Sites
CSS Cookbook
Forty’s Pocket Guide to SEO
The Design Funnel: A Manifesto for Meaningful Design
Ajax Design Patterns
How To Be Creative
Head first HTML with CSS & XHTML
The Woork Handbook
Ruby on Rails: Up and Running
Browsers And The Web
A Concise Guide to Archiving for Designers