I am new to CSS, and I am trying to figure out how it works. I am developing my web page www.projektowaniebim.pl and next thing I would like to do is to play with my background.
And here is my thkinking process and understanding of it, tell me if I am right:

1. In content.css in body i entered parameter background: #something - (I don't know actually if the value I enter have any influence on the look of the page, or it just have to be defined to be used ??-this is a question).

2. I want to have a color only on the sides not on the area with text (posts), so I should do something with my grid layout and create some kind of columns (??) and than apply the color to them ? I tried to add background: #something to layout.css and it applied it to the whole width, so it seems as if I had one big column (??)

Can you tell me if I'm thinking clear ? Or I totally don't understand the concept, if so than can you give me some kind of push in the right direction ?

You should start by taking a tutorial like the one at http://htmldog.com/guides/css/beginner/

every element can be styled and a child normally sits on top of it's parent element so if you colored both, the childs color would be ontop of the parents color. Think of it as a bunch of transparent sheets of paper, some cut into strips. You might paint some and leave others clear then you lay them ontop of each other.

That is my basic lesson, now go take a tutorial.