As said before HTML is the best place to start fallowed up by CSS. Keep in mind that the HTML standard is going to XML. You can learn HTML/XML and CSS at w3 Schools
W3Schools Online Web Tutorials
Once you have the basics of design and structure down I would reccomend learning Javascript or Client side VB Script. This will give you an understanding of variables and dynamic content processing.
Once you have an idea of how this works you can learn a Server Side Language for example ASP, PHP, C# etc. The newest thing out is AJAX, however microsoft may be tooting their own horn a little to loud about it. This will give you the ability to build database backed applications and many other features that make your website more interesting and interactive for your users.
And of course its always nice to learn some graphics design but a strong understanding of site structure is realy good, no matter how great the graphics if you don't have good structure your site might as well not be there.
I hope this helps.