Hmm.. To be honest I don't think that learning HTML is going to teach you much. You are better off learning PHP if you are into web development and such.
But if you want to learn about how computers operate I cannot suggest anything else than C in a system programming style.
Make a few silly applications a couple of times to get into the whole programming mind-set and then blast away reading on system API's for Linux systems.
You earn 2 things this way. First you learn how a computer manages memory,data input/output you understand the structure of memory (hello dear pointers) you will get a firm grasp of the various data types available (int,float,double etc. etc.) and what their differences are. You will use functions that are faulty and nobody told you that it has a security hole. (i'm looking at you getc()) . You will come across one of the most fundamental vulnerabilities buffer overflows and learn how to do some secure programming.
At the same time by doing e.g. socket programming you are forced into learning more about networks.
All the above will allow you to understand further down the road how encryption works and various network protocols and what and how and why is being used today. Oh and did I mention that by now you would know quite a few things about the UNIX OS? How the filesystem is structured, an abundance of system tools and more.
All these provide VERY SOLID foundations for anything else you might want to do later on.
After that you can go over to Java or C++ (I suggest java first) if you want to do some OO programming.
I am certain that people lean HTML or some shitty script language and get all kind of bad habits out of it that are very difficult to get rid off when you have to. I say start from the bottom up, not from the top. It'll be so much easier to learn HTML if you know how to do the rest first.
Now that I'm saying bottom if you find out you are into programming check out the MIPS assembly language, it has fairly simple instructions as a processor and is very well documented and there are quite a few simulators available (MARS comes to mind).
It might be just me, and I could be very wrong with those suggestions, but I am a strong believer that you will never learn how to swim if all you do is wet your feet.
Edit:
The book you go by the way is pretty good, but you must first understand how something is made before you try to dissasemble it.




