IE9 font size slightly larger than Chrome
 

Please view this site in Chrome & IE9.

In Chrome, the navigation LIs are placed within the header area.

In IE9, the font size is slightly larger, resulting in the UL being forced downward partially outside the header.

Here is a zoom comparison:
http://i112.photobucket.com/albums/n...ps8218dfb5.jpg

Yes. Browsers from different manufacturers are not identical, and there are small differences in rendering. If you code too tightly then you will run into all kinds of small dimensional differences that can break a page. So just allow a few pixels slack and you will not have a problem.

Thanks CobolSaur

If your website in question is too dependent on it's current code, you could always make browser specific code. That way you could manually make IE9's text smaller fairly easily.

I much prefer COBOLDinosaur's advice, to allow a little slack.

You can just use CSS to tell browser to use some certain font and size.