I think white space is so very important in web design.
There are two ways to look at white space (at least, I think so). First, you could say that white space is used to separate elements of a page – basically we use space between content elements to separate them. The second way you can look at white space is to ask yourself the question “does this page element help my design?” If it obstructs your overall message then by all means remove it. That’s more of a relevance issue but you get the point.
I’m trying to communicate that we should always evaluate whether something is important on a page and if it is, use white space to make it obvious. There is a good article about this at Design Matters.