Without being sarcastic, the answer depends on what is in the header and footer, and how they were created.
The layout of pages on your DotNetNuke are determined by your skin file. So, the best answer is that you'll want to edit your skin file and, possibly, the skin.css file.
Most of the "standard" items -- menu, logo, date, login, user, copyright, etc. -- are "skin objects" that can be placed in the skin file. You can control their behaviour by specifying attributes. You do this in the skin.xml file if you create an HTML skin, or directly in the ascx file if you use that approach. You may also edit the skin.css file to style the various items.
All of this falls under the heading of "Skinning" so you might want to read up on that topic. There is a document on this site that can be download. There are books that you can buy. There are some superb tutorials at DNNCreative.com on skinning and a host of other topics related to DotNetNuke.