HTML Frames Question

I am currently working on a website and would like to have the middle portion of the site change from new html page to new html page, while the top and bottom sections remain static, much like the the following site:

http://www.renata60.com

I know this is probably a frames question and i dont usually use frames, so i am not totally sure how to go about this. I made a top, middle and bottom frame in dreamweaver, but then i had trouble aligning the three sections so that they are flush with eachother and so the viewer can’t notice the frames, whereas the site above, the top and bottom portions stay the same, while the middle section changes and all the portions remain flush and aligned properly.

Any help would be greatly appreciated, thanks!