Domain validation: Suitable for small sites. In order to be issued, you do not need to send documents and it is validated only by email. Users will understand that you have an ssl at your site if they see in the address bar a small lock, an https instead of http, depending on the browser.
Organization validation: Users will share their financial information with you easily, so you will make more sales. You need to supply company documents for authentication and it can take up to three days to complete. Your site visitor will see https in the address bar and a lock. If he clicks on the lock, he will see some of your company's information.
Extended validation: High information security, high protection. Clarifies that the domain name is directly linked to your company and by this your user is protected from phishing attacks. It requires a longer checking process before it can be authorized. The user will see https, a lock, a green bar in the address bar. An example of an extended validation ssl site is https://www.pointer.gr
It is essentially a security system for information (usually of financial nature) relayed from a site to a user-buyer. That information is encrypted, so that no third party can track or intercept it.
Depending on how powerful such a system is, the cost of an SSL certificate is affected respectively
1. The user-buyer's Browser (Internet Explorer, Safari, Firefox) checks the certificate so as to 'make sure' the site it is linked to is authenticated
2. The Browser determines the encryption type so that it can use it along with the host web server of the site in order for only the two of them to 'understand' it
3. The Browser and the Server exchange unique codes to be used during the encryption of the information
4. The Browser and the Server now interact in encryption mode; the browser shows the respective icon, thus the web pages are considered safe.
If a site has a certificate then it should also have:
If your page at any time contains sensitive information, such as credit card numbers or private data/information you have to secure it by means of an SSL certificate.
Clients, current or potential, will not trust your web page without such a certificate. According to official surveys, 70% of online buyers at eshops have interrupted a business relationship because the respective shop didn't have SSL.
The features of a Domain validation SSL are: