Can I secure multiple subdomains with a single Certificate?
An SSL certificate is issued to a fully qualified domain name (FQDN). This means that an SSL certificate issued to "secure.freessl.com" cannot be used on different subdomains, such as "www.freessl.com". To get around this restriction we have available ChainedSSL Wildcard Certificates. Wildcard Certificates allow you to secure multiple subdomains on the same domain name, thereby saving you time and money, and of course you do not need to manage multiple certificates on the same server.

So with a single certificate issued to *.yourdomain.com you could protect:

www.yourdomain.com
• secure.yourdomain.com
• etc.yourdomain.com
Courtesy of FreeSSL.com!