I've been looking into content ratings for websites recently, mainly because certain clients have mentioned that they can't get our sites on their internal network.
Whether that's the problem in this situation or not is another matter, but it's worth investigating anyhow.
After a quick look on IIS I noticed that you can edit the ratings of your site, but before I began to fiddle I thought I had better find out more about these ratings.
Clicking on 'more info' in IIS content ratings section I went to www.rsac.org where I found out that the RSAC no longer exists. It is now part of the Internet Content Rating Association (ICRA).
They have a section especially for webmasters on the different ways of applying content ratings to your site. Included are instructions for Microsoft IIS web servers and Apache servers. I've linked to the webmasters section below.