What does learning assembly language mean?

So right now, learning CSS is pretty difficult. But luckily CSS specs have gotten pretty similar over different browsers, so its not terribly difficult even though some things are not exactly perfect.

But Assembly Language is rather straight forward, but the difficulty is that "assembly" is really a hundred different languages that depend on the specific processor architecture you are running on, and how that platform operates.

They are really orthogonal issues in the end, and comparing them is like comparing apples with automobiles.