I always wondered when browsing around that for some sites a green address bar is shown when using https, where for others it’s just the normal behavior. Green address bar sites are using something called an Extended Validation Certificate (EV Cert).
From Wikipedia:
An Extended Validation Certificate (EV) is an X.509 public key certificate issued according to a specific set of identity verification criteria. These criteria require extensive verification of the requesting entity's identity by the certificate authority (CA) before a certificate is issued. Certificates issued by a CA under the EV guidelines are not structurally different from other certificates (and hence provide no stronger cryptography than other, cheaper certificates), but are designated with a CA-specific policy identifier so that EV-aware software can recognize them.
The criteria for issuing EV certificates are defined by the Guidelines for Extended Validation Certificates, currently (as of May 2012) at version 1.4. The guidelines are produced by the CA/Browser Forum, a voluntary organization whose members include leading CAs and vendors of Internet software, as well as representatives from the legal and audit professions.
The Extended Validation Certificates do require you to provide more information in order to obtain one.
- You must be a valid and verifiable legal entity (Government agencies, Corporations, General partnerships, Unincorporated associations, Sole proprietorship's).
- The employment and authority of the person placing the certificate order must be verifiable.
- A legal opinion letter (from an Attorney, or Accountant) may be required to confirm that the requester has the authority to obtain SSL Certificate(s) on behalf of the company
- The entities must have a conformable physical existence and business presence.
Don’t know if this really makes your website more secure, it certainly makes the certificate a lot more expensive 