Pixels vs. Points in HTML/CSS

Question

When creating an HTML page, should I specify things like margins with pixels or with points in CSS?

Is one of them considered to be better practice than

Answer 1

I use pixels for nearly everything.

For me, it "feels" like I have more precise control.

For the few things that I need to dynamically resize with the window, I use percent.

EDIT:

What is "em"?