good thing to think about; not so good to implement:

• Unless you're willing to also do the jiggeryjoggery of learning the user's screen size, you're going to be shooting in the dark (Your specified table-size may be a bad match for the user's device: 2400x1800, 800x640, 320x200, WAP....)
• Browsers' font-sizes (in pixels) are inconsistent. Code a simple screenfilling line (with a mix of chars or real words) for one -- say, IE 5 or 6, and then open the same .html with FF or Moz or Konqueror. Then spec a different font-family and look again
    or....
• Proportional fonts -- even in the same nominal size -- do not necessarily allocate the same width in pixels for each char across fonts.
• and arguably worst implementing this except with css (at least, by any means I know) is going to royally screw those with vision impairment, who use local style sheets to cause rendered text to appear in larger and/or more contrasty fonts.

That said, if you have the option of using a fixed-width font, that could provide a comparatively easy and (to those who are vision-challenged) perhaps_acceptable solution.