RapidSSL Wildcard certificates are best suited for small and medium capital e-commerce web sites.
RapidSSL WildCard: Secure an unlimited number of sub-domains with a single SSL certificate on a single server. With a RapidSSL WildCard SSL certificate issued to *.yourdomain.com, you can protect the following FQDNs:
Key Features and Benefits of RapidSSL WildCard Certificate
Assurance of free unlimited reissue for 24/7/365
A cost effective multiple sub domains security