W3Schools is a great place to start learning the basics.
Truthfully, you are just going to have to dig in and get your hands dirty. That is the best way to learn because you could memorize tags and rules all day long and it won't help you in the end.
I suggest just getting a text editor like Notepad and typing content directly into it and save your file as a .html file. Then go to open it (or tell it to open the file with your favorite browser) and check out the results. This is the best way to learn what each tags do and how they affect your content.