If you want to create a website, the absolute minimum you must know is HTML (or xHTML). To make your site pretty, use CSS and make things more and more beautiful, use AJAX and graphics.

Learn HTML/CSS and many other web programming languages here:
W3Schools Online Web Tutorials

Learn more here (for inspiration, hacks, etc.)
http://www.devlisting.com/

If you want to be a blogger, better read:
Make Money Online with ProBlogger Blog Tips and Copywriting tips for online marketing success from Copyblogger

Kenpachi Rocks!