Thank you, I see what you mean but my question was not very clear. I will try to rephrase it:
I have a menu bar at the top of the main page (included form a PHP page)
The main page is divided in 3 sections which I have done with a simple table with 3 cells
When I click on any of the menu buttons to open a new page I want that new page to appear in the middle cell of the 3 in the table.
hope that makes sense