If I understand what you want correctly then this is something that all beginners seem to ask and is the actually the wrong way to go about it
Unless you are doing a simple content swap as Eric has shown you you really don't want to create a one page sites where all your content is loaded into that one page.
Just create a new page and navigate to that new page like everyone else on the web is doing. Long gone are the days of using Frames and following that approach.
It takes little more time to load the whole page once the css has been cached so there's not really any benefit staying on the same page but there are many drawbacks. For site upkeep you can keep repeating sections in includes (SSI) so that you only need to maintain them once.
Also take care in setting heights for fluid content . You will rarely want a height on your content container and if you do then you will need to control the overflow so that it doesn't overflow. Of course that will leave you with scrollbars on everything should content be too large or perhaps the user has larger text than you bargained for.
Web pages should be as fluid and as flexible as possible. Let the page breathe and let it shrink and grow as required.