Much of the theming work -- layout, colors, and fonts -- is accomplished via Cascading Style Sheets (CSS). Our base themes, AdaptiveTheme and Pixture Reloaded, provide a boatload of CSS files totaling about 3,000 lines of code.
We add another 200+ lines of CSS to further tune the appearance of the site. This custom CSS is found in $D7/sites/www.iac.org/themes/iac/css/local.css.
