This is a simple plugin for Fiddler 2/4 that will allow you to view the certificate information of an HTTPS request. One of the few things I've needed from fiddler that it didn't have.
Just compile it and place the resulting dll file in the Inspectors folder under your Fiddler install folder.
You can also download the library from: http://www.frakkingsweet.com/Downloads/Vecc.FiddlerCertInformation.zip and place the dll in the Inspectors folder, underneath the Fiddler install folder.