WHY SHOULD WE LEARN HTML?

HTML is the language that web pages are written in.

Why learn HTML? It is possible to design websites without knowing it,isn't it?
Absolutely.
First, what's HTML? It's simply Web page coding interspersed into the text
and images; browsers interpret or display it into the displays we see as web
pages. Let's back up: like many people, I started out with a web authoring
program with a graphical interface (WYSIWYG, or "what you see is what
you get") that automatically wrote the HTML. When I started, I didn't know
much about building websites, much less web design, and I had to fix a
website now. That meant surfing around the Web looking for any help I
could get. I found a program I could work with, and stuck with it for years.
Well, of course, the time came when I had to move on from my simple
program. Events conspired against me. I got two clients in a row: one,
a die-hard hand-coder who wanted a redesign; the other had a website
rejected by Yahoo and only three weeks left to appeal. To paraphrase, one
wanted very clean HTML code and, for the other, I designed a very complex
layout that "broke" in my simple program — and, of course, he loved it and
there was still the three-week deadline. I went immediately to hand-coding.
I can't say it was easy, or fun. I tried staring at the HTML code(!). And I
tried studying part-time at the usual online sites, but had a tough time
getting through all the jargon. (I'm still not sure why people trying to teach
you something new assume you understand the jargon ... as if we somehow
understand it by osmosis). At any rate, I made the deadlines and lived to tell
the tale, and both clients were very happy with the results. The first reported
that her income doubled overnight due to the redesign. The other was
promptly accepted into Yahoo, and has been expanding his reach and client
base ever since. But a funny thing happened: I continued to hand-code, and
somewhere in there, it became my preferred method of building websites.
The sheer control hand-coding HTML gives you is a breath of fresh air, and
knowing what the HTML codes are doing — or were never meant to do — is
wonderful. Knowing that your pages will not "break" or display incorrectly
is great. Knowing that you can code HTML to display properly in a variety of
browsers is a relief. And knowing that the program you're using will not
mess it up is priceless. Later on I got another WYSIWYG program, but that's
another story, and am now in the middle, using both as preference dictates.
It's kind of like being ambidextrous — being able to use both hands.