YSlow is kinda dumb. It looks at the URLs in your site and if it recognizes one that is from a known CDN it knows you have a CDN.
So if your URLS are. domain.vo.llnwd.net or domain.com.edgesuite.com then it knows you're using Limelight or Akamai.
So it obviously doesn't know what the CoralCDN url looks like. Also even if you're using a CDN and you CNAME to it, YSLOW doesn't know.
For example. static.domain.com pointing to your CDN Host.
Don't Rely on YSLOW to know you're using a CDN.
The way Coral CDN works is this:
you add: .nyud.net to the end of your URL and then it will deliver the content from the CDN cache. If Coral doesn't have it in cache, it will go to whatever the rest of the URL is to get it.
Example: http://www.cnn.com (is the source)
http://www.cnn.com.nyud.net (Coral CDN cache servers)
Coral is ok, it's a FREE CDN. If you are doing less than about 100-200GB of content delivery /month, Coral might be fine. But if you're doing more than a couple thousand page views a day or more bandwidth, then Coral will probably not be able to keep up.
- Mike Colburn