Look for one of these in your css file:
input, textarea
I'd also suggest downloading firefox (
http://www.mozilla.com/en-US/firefox/ ) and firebug (
https://addons.mozilla.org/en-US/firefox/addon/1843 ) which allows you to change all CSS in your browser.
You can click on inspect, hover your mouse over the search box and left click once. It'll select that part of the html code and from there you can navigate up or down thru the CSS layers.