You can create a reasonably rich web site in a short time with absolutly no knowledge of HTML, PHP, mySQL or any other technology traditionally associated with the web.
As a bonus, Joomla creates web sites where you can give rights to certain users to modify the content of (selected bits of) the web site without them having to "re-programm" the web site. It has built in editors that allow that kind of interaction as part of the website itself.
Two weeks ago I thought I'll never design and build a web site in my life.
Four days ago I just finished one (hosted here on x10Hosting) and I'm now waiting for feedback from the people who asked me to build one.
And I do have a day job and my weekends are pretty full.
I estimate I must have spend 10-12 hours in total.
All thanks to Joomla.
Go to their website as shown by zen-r above and follow the "Absolute Beginner" guides/tutorials.