Why validate web pages?
http://validator.w3.org/docs/why.html
Web Content Accessibility Guidelines
www.w3.org/WAI/WCAG20/glance
In praise of CSS-based designs - apply different stylesheets to the same page for amazing results!
www.csszengarden.com
Minimalism in Web Design
http://sixrevisions.com/web_design/minimalism-in-web-design-a-guide
Examples of minimalist designs
http://sixrevisions.com/design-showcase-inspiration/40-beautiful-examples-of-minimalism-in-web-design
Choosing colour schemes
http://colors.napcsweb.com/colorschemer
Designing for mobile devices
www.webcredible.co.uk/user-friendly-resources/web-usability/mobile-guidelines.shtml
Web Performance
www.webperformancetoday.com/2010/06/15/everything-you-wanted-to-know-about-web-performance
Usability Guidelines
www.usereffect.com/topic/25-point-website-usability-checklist
Basic guidelines
http://websearch.about.com/od/beginnersguidetoseo/a/tenstepsseo.htm
Advice from Google to webmasters
www.google.com/webmasters/docs/search-engine-optimization-starter-guide.pdf
What is Open Source?
www.opensource.org
Sourceforge, the leading resource for Open Source software development and distribution
http://sourceforge.net
PHP, the popular Open Source server-side HTML embedded scripting language for web developers
www.php.net
MySQL, the popular Open Source database
www.mysql.com