Dont worry. Its telling you that the communication between you and the web server is secure. However, the certificate that helps to do this is expired.
This is one of the idiotic messages from IE. It gives a warning telling you that you are safe
You should notice that the webpage address is https:// rather than http://
In the address bar, near the icon of the address bar, you will notice a button like area, which when clicked will give you the site information.
If you need more info, read about SSL and https from wikipedia