Different background color for content area on one page

http://annaustinyoga.com

I want just the home page to have no background in the content area, and I see using Firebug that the article id for the home page content area is “post-4”, but despite all my efforts at changing the css for that article to "background:none;" I have had no luck. I must be using the wrong selector, but no variation I have tried has worked…