I am currently using Green Apples theme (http://theorganicsister.com). I'd like to make the whole thing thinner - basically decrease the size of the middle column so all three columns are centered on the page with a bigger border on the outside of the columns. Also I'd like to adjust the header accordingly.
As an example of what I mean here is one theme that has been stretched:
And the same theme, not stretched:
So how do I adust the size of the middle column and the header? And when I do that will the left and right sidebar stay where they are or come in close to the middle column?
(I hope this makes sense. I'm not sure how else to explain it.)