I was wondering how I would go about opening a open within the index.html page like in the div layer

I have a 4 column site and for the middle of the index.html I wanna open pages

so it kinda looks like below.


HTML Code:
------------------------------------
|                                  |
|                    Header        |
------------------------------------
|------||--------------------------|
|  NAV ||                          |
|        | |             Middle    |
|        | |                        |
|        | |                        |
|        | |                        |
-------- |                          |
|  NAV | |                          |
|        | |                        |
|        | |                        |
|        | |                        |
|        | |                        |
|        | |                        |
------------------------------------
|                    FOOTER       |
------------------------------------
I wanna open the links in the NAV to the middle but without using iframes or using php