Add BuddyPress Styles to a Theme
BuddyPress 1.7 adds the ability to use any WordPress theme. The theme compatibility has a base style sheet that helps format the BuddyPress content. The styles may not be perfectly suited to your theme.
It’s very easy to add your own styles. If your theme folder has a sub folder called css you only need to add a stylesheet buddypress.css to this folder and BuddyPress will use this file overriding the BuddyPress styles. If the css folder is missing just create one and include the file inside. You can copy the buddypress.css file from the BuddyPress plugin folder and edit or create your own.
Theme Developer:
If you want to ship your theme with extra styles to support BuddyPress add the BuddyPress styles to the buddypress.css file and include it in your theme. Do not add the BuddyPress styles to your style.css file. This will ensure the styles are only loaded when BuddyPress is activated and will override the default styles supplied by the plugin.
Prefix your styles with #buddypress to target the areas of BuddyPress content.
#buddypress .activity-content { }
*NOTE As of 1.8 you can place the file in /my-theme/community/css/ or /my-theme/buddypress/css/