I always set the font size to 62.5% for the body in my css file, ie
Code:
body {
font-size: 62.5%; /* resets 1em to 10px */
}
then in my content div set my font size to, say 1.1em
Code:
#content {
font-size: 1.1em;
}
By using em values for specifying font size you allow viewers to easily scale text if it is too small. You can either have a text size selector on your site or just let viewers adjust the text size through their browser.
This will keep your site accessible whilst still giving you the control you want of your initial font sizing.