How specific to be when coding CSS???

Very good question. You know what CSS stands for: Cascading Style Sheets. The name basically means that rules will cascade over each other, with some being overridden by later rules or by more specific rules.

One of the rules of this cascade is that specific selectors override more general selectors. That is, a selector like #gallery li a p will override #gallery p because the former is more specific. There are other a few rules too; for instance, ID selectors (#gallery) will override class selectors (.post). Guil discusses a lot of these rules in his CSS Basics course, which you should take soon after you finish this first course.

As a rule of thumb, be as general as you reasonably can. Overly specific selectors are much more likely to break as you make edits to your code further down the road, they're much harder for other developers to understand, and they're also slower for the web browser to render (though this last one is becoming less of a concern with the amazing browsers and hardware we have these days).

Hope this helps! And welcome to Treehouse! :)

EDIT: I said that selectors that got too specific are bad. The opposite is also true; if your selectors are too broad, your styles can leak out of their rules, and that's not fun at all. Fortunately, it's a lot easier to prevent broad selectors than specific ones; just try to scope any tag-name selectors you have (instead of h1, select by #article h1).