Ok...I finally solved the problem so I tought I should share it in case there is others that have the same problem.
I finally found the magical formula in the css that made my top and bottom cells to high. It was the standard body line in reset.css(line 29 for me) that addet 1.25em to the line height(regadless if ther is any tekst or not, but that just the way css works I suppose:-).
My sollution was to make a new div id just for my tables on the front page where I sat the font size to 0 px and set the lineheight to unchanged. Other tekst in the table I formated with HTML in the editor and my tables get the look I want.
I can also add that I installed Firebug to help me find the magic css formula.