What do you mean by "Every time I do, the "blog" and "contact" divs are effected and get moved down"?
Do you mean that the output in the browser actually gets moved down?
The first thing that I recognize is that you css definition for the #extras div is not being closed!!
In most cases when I have trouble with css a invalid css definition is the cause for the problems.
Try using a xhtml validator like the http://validator.w3.org/
This (in most cases) will help you identify problems, that are caused by e.g. not closed div tags or wrong definitions!