From awcolley.com

WebsiteDev: HTML Markup and CSS Style

HTML / CSS

I periodically check random pages from my websites using these official W3C validation services, to make sure my websites adhere to Markup and CSS standards:

• W3C Markup Validation Service
• W3C CSS Validation Service

Other useful online validators:

• W3C Link Checker — check all links on a page to make sure they are still valid.
• Robots.txt Validator — check the validity of your robots.txt file. Also provides links to pages that explain how to use a robots.txt file and the syntax it requires.

There are many websites providing HTML and CSS reference documentation; my favorite one is blooberry.com:

• Index DOT HTML
• Index DOT CSS

The definitive, though sometimes obtuse, documentation for HTML and CSS is at w3.org:

• HTML/XHTML Markup
• CSS
• Learning CSS

To display characters from other languages, mathematical symbols, and various other non-alphanumeric stuff, you can use HTML "named character references":

• Named HTML Character References
  • alphabetic order
  • numeric order

Most fonts provide even more characters than are supported by HTML's "named character references"; you can reference those using HTML "numeric character references":

• TBD

Some characters are not directly supported within URLs (e.g. a space), you can get around that by using URL encoding:

• URL Encoding Chart

Color:

• HTML / CSS Defined Color Names
• Web Designer's Color Card

Here are a few websites dedicated to tips, techniques, and best practices for website design:

• A List Apart — "explores the design, development, and meaning of web content, with a special focus on web standards and best practices."
• Creating Websites FAQ — boutell.com, purveyors of quality web resources since 1993
• Position Is Everything — explains some obtuse CSS bugs in modern browsers, provides demo examples of interesting CSS behaviors, and shows how to "make it work" without using tables for layout purposes.

Here are webpages with specific information related to website design I found useful at one time or another:

• Table Centering using HTML or CSS
• Center a Table with CSS
• Centering Things (CSS)
• One-pixel Table Border with CSS