stylesheet_betterCategoriesEzInfo.css, around line 12:
Code:
.betterCategories a, .betterCategories a:visited,
.betterDocuments a, .betterDocuments a:visited,
.betterEzpages a, .betterEzpages a:visited,
.betterInformation a, .betterInformation a:visited,
.betterMoreinformation a, .betterMoreinformation a:visited,
.betterBestsellers a, .betterBestsellers a:visited {
display: block;
background-color: #fffffe;
border-top: 2px solid #ffffff;
border-bottom:2px dotted #b5b5b5;
padding: 4px;
font-size: 0.9em;
}
Add the line in red, and adjust to taste.
I think this is the wrong issue to solve, however; making the text smaller makes it harder to read. You do not appear to be using the right sideboxes at all, and if you turn off the right sidebar, you can make the left sidebar wider without sacrificing font size or main content area.
Admin > Configuration > Layout Settings >
Column Right Status - Global
Column Left Width
Column Left Boxes Width.