It's been kind of a long time since I built a website but I think informations from three years ago still applies in some way to current site building. Yeah you should learn HTML and CSS, this will keep your webpages clean and there is actually very little you can't do with it, as far as the "webdesign" part go. A good site I used was this :
It has PLENTY of info and will teach you mostly everything you need to know about HTML.
The second part of your learning will be CSS (Cascading style sheets). These are "styling" codes to tell the browser how your HTML elements should look like. Don't worry if it sounds complicated, everything is very simple and well explained here :
And yes, you should also learn a server-side programming language as PHP. It will allow you to build dynamically generated webpages with some lines of codes using variables. It it very powerful and will save you hours of hard... you can learn it here :
And how to install it :
Notice that ALL the link I gave you are from the w3schools as it is a very complete source and helped me to learn everything I used in a nice and simple step by step way. The lessons are covering more and more complex aspects of coding with each new lessons, giving you better desing tools for your site.
On a closing note, you could also learn MySQL if you are aiming for a complex site with need for database access, otherwise, stick to the four mentionned above.
Hope this helped,Edited by Schaezar - 4/5/11 at 2:16am