It depends on what your site will be – if you are looking to write a blog with your own domain but not be connected with a blogging service site like blogger then you can register a domain with a webhost, such as myblogpage.com get some web space from them (a hosting account) and then install Wordpress (www.wordpress.org) your site will then be easy to update and customise without any/much web design know how. Example my blog http://www.fromthefrontend.co.uk
If you want to do something more advanced or actually learn the skills needed I recommend getting a good HTML and CSS book to start with such as CSS mastery or the CSS anthology. Check books from publishers like O’reily and Friends of ED.
If you stick at it HTML/CSS basics can be learnt in a couple of weeks and enough to build a basic site but you’ll need to pick up some Server Side scripting like PHP to do anything advanced.
http://www.w3school.com is another good resource.