In my opinion the best way to learn HTML is a hands on approach. Start viewing the source code to web pages (Firefox: View->Page Source). Look for "tags" which will always be inside of a pair of < >'s. Try and figure out what that tag does and how it is represented on the page. I recommend turning of CSS Stylesheets at first, so you can see the page before it is "stylized". It's good web-practice to make your pages accessible as possible. Some browsers may not have "CSS" support on, and your web page could possibly look like ass. You should make your web page "usable" then go back and tweak the looks. That is to say, you can do things many ways, and they may (or may not) render to the same display.
You're simplest website should look like this:
You'll get the hang of it, its a very simplistic syntax. Notice all tags will start with a < followed by the name of the tag. and then they will eventually end with / followed by a >.
Many tags have the ability to contain text or even more tags. That is what you see with the paragraph tag:
Notice the name of the tag is repeated in those instances. (</p>).
Some tags will not have that, such as the image tag:
Notice that they (as well as the other tags) can have attributes (such as "src" , or source for refrencing a URL/file), that are specific to the tag itself, as defined by the specification... that is why you should always set which specification of HTML you are using, and you will see people exclaiming "XHTML Compliant"http://www.w3schools.com/Xhtml/xhtml_dtd.asp
for more info on doctypes... And basically the best HTML refrence site.