Generally, in these situations you could use the tool FireBug to inspect elements and view the css entries.
The tool FireBug that is available in browsers such as FireFox and Chrome could be used for this purpose. With FireBug you can inspect an element in a web page and find out its css entries and in which file the entries are located. You could even change the css entries to see how it affects the look and feel of your site. Once you are satisfied you could incorporate the changes in the actual file.
Review the document
http://docs.joomla.org/Tutorial:Using_F ... la_Website for more information about how to use FireBug.