Question

I just took over a new project. The guy before me coded a lot of:

div#headertop {
    margin: 0 auto; 
}

Is this really needed or is this the default anyway?

Answer 1

All current browsers have margin: 0 as the default margin for div elements.

margin: 0 auto is not the same thing — if the div has a fixed width, margin: 0 auto creates a div that is horizontally centered in its container.