Looking at your CSS, it looks like adding the following code to your 'styles.css' file may solve the problem.
#navBar {
float: left;
}
.contentContainer {
float:right;
}
Also, your page does not use a Doctype Declaration but should use one.
Please see here for details: http://www.w3.org/QA/2002/04/valid-dtd-list.html
Looking at your code, the most appropriate one to use might be XHTML 1.0 Transitional, in which case, put the following code at the very top of your HTML document, immediately before the opening <html xmlns="http://www.w3.org/1999/xhtml"> tag.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Steven Speirs
SimpleViewer Support Team