Changing font sizes in style.css

Found a few sites such as alexking which have some very useful styles for those of us who are graphically-challenged. Some of the fonts in the style.css files are just a little larger than I like. They will show percentage font sizes, but where is the default or “100%” font size controlled? In other words, how do I make every font a little smaller by making the default size smaller? Here’s a brief excerpt as an example.
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body { margin : 0; padding : 0; background : #e8e8d1; color : #111; text-align:center; font-family: Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;}
h1, h2, h3 {font-family : “‘New York'”, Utopia, Georgia, “‘Times New Roman'”, Times, serif;} h2 {letter-spacing: .07em; border-bottom:1px solid #c00; text-align:right;}
p{text-indent:2em; line-height:1.4em;}
form {margin: 0; padding: 0;}
input, textarea {background-color: #eee;border: 1px solid #aaa; font-size:95%; }
blockquote {font-size: 90%; color: #777; padding-left: 23px; border-top:2px solid #ee7; border-bottom:2px solid #ee7;}
Thanks.