Unable to change Style CSS

Hi,

I need to change the header size but my style.css only displays this:

/******************************************************************
Theme Name: SimpleCorp
Theme URI: http://www.s5themes.com/theme/simplecorp/
Description: SimpleCorp – Check SimpleCorp Documentation in case you need directions or get support from Forum.
Author: Site5.com
Author URI: http://gk.site5.com/t/568
Version: 2.1.5

License: GPL
License URI: http://www.gnu.org/copyleft/gpl.html
******************************************************************/

@import url(“library/css/main-css.css”);
@import url(“library/css/768.css”);
@import url(“library/css/320.css”);
@import url(“library/css/480.css”);