Can't change #header css

When i try to change the header to a custom image by changing the CSS I can find the existing css code in Firebug but i cant find that code in the theme’s css.

code seen in Firebug:
#header #search-bar {
background: -moz-linear-gradient(center top , #098AC6 0%, #098AC6 15%, #055478 100%) repeat scroll 0 0 transparent;
filter: none;

However I can’t find it in the file to change. I have also inserted css BG image codes in other sections and it worked, just not the #header #search-bar

Thanks,

http://ww.wp.xz.cn/extend/themes/frisco-for-buddypress/

[Moderator note: Continue here http://ww.wp.xz.cn/support/topic/buddypress-frisco-theme-changing-header-with-css?replies=5 ]