http://www.w3schools.com
W3Schools is a great reference for anything web-scripting related. Although it seems to be geared more toward advanced users than beginners, they have some basic tutorials and the References Tag Lists are great for anyone. They even have some online quizzes to test your skills in standard languages such as HTML, CSS, and JavaScript
http://www.htmlgoodies.com/
HTML Goodies is one of the best resources online for all your web development related needs. The site includes a huge variety of articles, tutorials, and examples that span from the non-technical side of website building to advanced subjects such as DHTML and CGI. Everything here is in an easy to understand format so even someone completely new to the web development world should be able to learn and understand with ease.
http://www.sitepoint.com/
Get and recieve help on the basics to learning how to monetise your website. Also learn from the best people around who make a living off of the web.
http://www.w3.org/
The World Wide Web Consortium (W3C) sets the standards for all our internet development technologies. They host a massive quantity of articles and links related to web-development, but most are very hard to understand. They do have some good tips on creating a website that meets the standards of the World Wide Web, and they even have
tips for webmasters and some
source validators that parse your code and check it for validity.
http://forums.webdeveloper.com/ If you ever have a question about anything web development related that you can't seem to find anywhere, this is the place to go. Hundreds of fellow web developers visit this site daily posting and answering a wide variety of questions. You'd be surprised at the tricks and shortcuts you can learn by just reading through the archives!