This support forum is only for those who have free hosted WordPress.com blogs that they have purchased a CSS upgrade for. CSS editing is theme specific and the versions of themes we have at WordPress.com are not the same as the WordPress.org versions of the theme.
If and only if you are referring to a free hosted WordPress.com blog wearing the Chateau theme that you have purchased a custom design upgrade for then please post an active link to the blog in question. http://support.wordpress.com/com-vs-org/
If you are reaferring to If and only if you are referring to a free hosted WordPress.com blog wearing a different theme that you have purchased a custom design upgrade for then please post your own thread > http://en.forums.wordpress.com/forum/css-customization#postform
If you are referring to asite that's not hosted by WordPress.com like the one linked to your username you must post to http://wordpress.org/support/