Add a style (CSS)

1. Open \theme\standard\config.php (assume you are using "standard" theme)
2. Find the last element of $THEME->sheets (should be css3 if you have not done anything yet)
3. Open \theme\standard\style\css3.css and add your css code
4. Goto \moodledata\cache\theme\standard\css and delete all files (anyone have a better way?)
5. Done