The answer to this question is dependent on how complex you want to make your site.  If you want to build a basic Web page with simple text and a few pictures, the ability to use a simple WYSISWYG (pronounced wiz-zi-wig) HTML editor and some basic HTML knowledge is all you really need.  On the other hand, if you plan on building an on-line store that could have thousands of users, I recommend being well versed in HTML, CSS, JavaScript, AJAX, PHP, and MySQL.  You will also want to use more advanced Web design software, which can be rather expensive.  If you have not developed a professional Web site before, and you plan on using it for business purposes, a professional web designer should be consulted.

There are a number of excellent Web sites that help people who are just getting their feet wet in Web design.  Here are a few: