These pages at gentry.metr.ou.edu, use my style sheet gentry.metr.ou.edu/sheet.css, which currently contains: 
body { background-color: #eeeeee; color: #000000;
 font-family: "Trebuchet MS", Verdana, Sans-serif;
  font-size: medium}
p, b, em, ul, ol, td, hr {color: #000000; font-size: medium}
h2 {font-size: medium;  color: #666600}
h3 {font-size: medium;  color: #666600}
span {font-size: medium}
tt {color: #990000; font-family: monospace; font-size: medium; font-weight:bold;}
pre {color: #990000; font-family: monospace; font-size: medium; font-weight:bold;}
A:visited {color: #005599}

I view these pages mainly with Firefox 1.5.0.4. Banging on Ctrl+ and Ctrl- easily adjusts the font sizes. Under Edit, Preferences, Content, Fonts and Colors, Advanced", I have both proportional and monospace font sizes set at the same value, which for me is 16.

The following are intended to be nearly the same size:
same same