WordPress Responsive Theme – Wheres the CSS File? A lot of people have broken sites and child themes after the recent CyberChimps updates to the responsive Theme. They can’t find the CSS style sheet anymore and I show you where it is plus 2 other great options to modify the CSS of your theme.
I am using a custom MVM Child Theme mod for my website that I had to adjust after recent updates as well. Child Themes are recommended in most if not all of my tutorials or I recommend making copies of every file you modify before and after. More Tips Tools and Tutorials from Allan at Mindvisionmedia.net
source