I want to have three columns, a 1000px middle column that is centered to the page and then a column on the left and right that takes up the remaining width.
I basically want something that looks like this:

Where the wrapper is 1000px and the two side spaces are half of the remaining total space.
You can easily centre an element with
margin: 0px auto. This will leave a space on the left and right of the element. If the element is inside another which takes up the entire width, then a background can be placed and centred inside it.An example might be:
Then the CSS would look like:
It wouldn’t be possible to put content either side of the #content div.