I suggest you jump right in - but a domain and some cheap hosting from the likes of namecheap.com - make sure the hosting has php/mysql - as it will mean you can do much more with it. Then create a simple site - start with just a 'Hello World' page, even if it's pointless, it will still give you a sense of achievement just to have your own website live to the whole world. Then use all the links above to help learn html first, then php/mysql. Try installing free software like phpbb (forum) or wordpress (blog) - you'll see how sophisticated they are, and how little know-how it takes to put together.
If you really know absolutely nothing at all about web design, a site called simplersteps.com (I think it's dot com) has a series of links to incredibly easy site-building tools (and also some software) that enable you to build sites just by dropping and dragging - and all online. Of course, sites made this way will never have the same kind of flexibility as a hand-built site, but I had a look at the links mentioned and they really WERE impressive! The simpler steps web also gave info on putting advertising on these sites - which can be done apparently, even though they were free. I'd seriously recommend taking a look. I build more or less by hand and was astonished at the high-quality results these online options gave. It also seemed amazing that it was all free and could easily be used to create an ad-carrying site. I've just looked it up - it is .com - simplersteps.com and seems to have a LOT of info for anyone with no knowledge whatsoever of the web. Really hope that helps and this message isn't too late to help you get started!!