If you know the height of the paragraph, you can specify a padding either on top or bottom of the browser window.
<div id="nav" style="padding-bottom: 50px">
<p style="position:fixed; bottom: 0; height: 50px">...</p>
Position fixed is not like absolute, it will always follow the browser window regardless of its parent element's position value. If you don't want to specify a height, then you adjust the bottom padding until the paragraph doesn't overlap with anything anymore.