Navigation Issues

[(¯`·._ Çh®î$ _.·´¯)]

For navigation on my site I'm putting a tree style menu on the left hand side of the page, and what I want to do is open all links directly in a center area of the page without affecting the menu, banner up top, and right side contents of my page, and not open all the links in a new window. I suppose this would be done via an iframe, but how exactly do I go about it?

[Twey]

<iframe name="contentwindow"></iframe>
<!-- ... -->
<a href="otherpage.jsp" target="contentwindow">Some other page</a>