If you have some extra $$$ pick up "Beginning Web Programming with HTML, XHTML, and CSS" from Wrox books (or check it out from a library). By the end of the book you'll even know some javascript. But if you don't have disposable income (or the library doesn't stock it), search online. Loads upon loads of HTML tutorials exist out there.
To do more than merely manipulate a WYSIWYG editor (e.g., Front Page, Dreamweaver) and do "real" web programming, you'll have to know HTML second nature.