Everybody developing css perhaps can distinguish between properties like background colors, fontsizes etc on the one side, against properties of the css boxes at the other side. In phpWebSite, the distribution of the properties are well organized. There are different style sheets for both cases. No matter in FireBug, that always shows the right reference. When you are not experinced with css box handling, be carefull to make changes too thoughtless. Especially regard the relative and absolute references coded for the various elements all belong together in a not quit easy overseen matter.
Whatever, we may also play with those. FireBug enables a view to the css boxes with the layout tab in the lower right side area:
Here you can see the css box model for the #container, ... and change.
One step beyond, also the dom interiors may be viewed (and changed).
That is of interest for everybody playing with javascript.