I would say that best thing to do is to go to the various languages web sites. For PHP, there is [http://php.net], for MySQL (and you will want to learn Structured Query Language), there is [http://mysql.com]. For HTML, CSS, stick with the specifications, [http://www.w3.org/TR/html401/index/elements.html] and [http://www.w3.org/TR/html401/index/attributes.html] (HTML/XHTML) and CSS [http://www.w3.org/TR/CSS21/propidx.html].
I have a tutorial that you might find informative, http://www.cavalcade-of-coding.info/html/index.php. If that doesn't help you, you can't to better than HTML-Dog [http://html-dog.com]. I would stay away from W3 Schools, at least for markup.
You can also learn a lot from bad designs (what not to do), so check out Web Pages That Suck and Jacob Neilsen's Alert Box Top 10 Web Design Mistakes of 2003 (they are still valid 6 years later).
Learn the value of validating your markup (HTML, CSS and WAI). Use semantically correct markup - leave presentation to CSS. Don't abuse tables. Don't use a WYSIWYG editor - especially if you want to do server side stuff. Use a good HTML editor, I like HTML-Kit for HTML, PHP, etc. A good stylesheet editor is a good idea too, I use TopStyle from Bradsoft.
The other thing you can do is install a web server on your computer. Then you can develop your sites and test them before putting them on a live server. Install PHP and MySQL, there are complete packages available, just Google for them.
If you have not already done so, dowload some browsers. Here's my current list:
Opera (default - Presto) - comes with DragonFly development tool
Firefox (Mozilla) - install Web Developer and Firebug extensions
Chrome (Webkit)
Safari (Webkit)
K-Meleon (Mozilla)
Multiple IEs (google for it - 3-6 come in one package)
You might also want to lurk in some of the Usenet developer groups:
alt.html, alt.html.critique, comp.infosystems.www.authoring.html, comp.infosysystems.www.authoring.stylesheets, comp.lang.php, comp.databases.mysql. You will want to get a news client, I like Xnews, and a good Usenet provider. I'm using eternnal-september.org - free and fast, but no binaries.
As far as hosting, someone mentioned http://000webhost.com. I use them for showing clients mock-ups. They are fine for a beginner.