Well untile recently i was wondering the same thing. But it is a personal choice :3 for me i started 1 side project in html/css so i could keep it up and work here on the forums if people have html/css questions i try and see if i can answere them. and then I wanted a new challenge so i started to do js. Thats only my story thou it really depence onto what you think is good for you
I have found that if I go too far too fast I lose some of the knowledge I had gained over the course. It might help to create a few websites of your own with just HTML and CSS to get familiar with it. I wish I had done that first, but I was in a hurry. Of course it ultimately depends on how much time you feel you have.