This is what I noticed. Netscape will display the text at 10px with just the declaration in the body selector, but in order for the text to be displayed in IE.6, I have to add the line in the table selector!
Internet Explorer doesn't correctly inherit the font size for TABLE tags. It seems to use the browser default font size for body text unless told otherwise. I've also noticed the same behavior with the H4 tag too, that most browsers, including IE-Win, size H4 tags the same as body text, unless you change the text size from the browser default.
So basically always set the font size you want for the H4 and TABLE tags because IE-Win doesn't inherit the size correctly.
You have to remember that IE6 was written many generations ago before the current web standards were developed. You need a version 7 browser at minimum to be able to get reasonable support of the 21st Century standards and a version 9 browser or better for full support of the standards.
The general rule is to design and test using a modern browser like Firefox or Opera. Once that's working it should work in all other browsers except, perhaps, IE. But then you know your code is good and you only need adjust for IEs quirks and bugs.