You can control all borders of a table with CSS. You may need to set "border-collapse:collapse" to have a single border between two cells but otherwise setting the "border" attribute of table, th and td should sufficient. What was your actual problem?
A quick googling even gave a CSS table wizard, e.g. http://www.somacon.com/p141.php (I just took a short look on it but it seems nice).
I always thought em was a relative unit depending on current font size. So 1.2em should render different on Firefox and IE since they use different fonts.
Don't tell people you use tables! Web designers will point and laugh at you for using tables. Fickle bunch, those web designers.
Chris: Yes, but the borders you control through CSS are still *different* to the 'grid' you can switch on in the html tag attribute - which I also need to control.
Todd: I think you are right - this might just be the text settings on my browser, viewed from another place it didn't look different.
Will: But it was for displaying a *table* of data - what am I *supposed* to use. 
Actually, I might be trying out a javascript 'grid', just for fun...
borders are style in a table. So you can control them on/off from the CSS. If you give an actual example of the two rendering you expect, it would help us to give you an answer.
em is good food for accessibility and helps to resize at the will. em++ I love them.
table for table of data is good. Do not worry for this.
Commenting by HaloScan
