source path of files published by asset manager from browser

How do you know the source path of a file published by yii asset manager?

I want to edit the sourcer css file for instance, but in firebug i js see

http:://localhost/site/assets/8e3f9c3/gridview/styles.css, how do i know wher the actual style.css file is for me to edit, i know i can override the selector from other files like main.css but i would rather modify the source.