Web Site Certificates

Can you please go over what Web site certificates are?
First of all, if a certain company or organization wants their Web site to use encryption and be secure, they must obtain a site (or host) certificate. If they don't, they will not be registered as a secure Web site. So, how do you tell if a site is secure or not? Well, we've gone over this before, but let's cover it one more time, just to be sure we're all on the same page. There are two things you can check on to find out if a site is secure or not. The first is a little yellow padlock in the bottom right corner of your Web browser. The padlock should be closed (locked) as well. The second is how the Web site's URL reads. On a secure site, the very beginning part will always be "https," rather than just "http." That extra "s" makes all the difference when it comes to security.
So, if you're visiting a site and you see either of those things, the site will have a certificate. You can view the certificate by double clicking the yellow padlock. Once you do that, a certificate dialogue box will pop up and you can read all about it. It will tell you the purpose of the certificate, who it's issued to, who it was issued by and when it expires. (If the site you're on just uses the "https" method, just double click in the area where the padlock usually sits. Doing that will bring up the same certificate box for you). For example, when you purchase something from online software store, the checkout page is secure. If you double click the padlock on that page, you will be able to see our certificate.
Another way you can view a site's certificate is through your browser's menu options. In Internet Explorer, go to File, Properties and then click on the Certificates button. The same dialogue box will then come up for you. In Firefox, go to Tools, Page Info and then click on the Security tab. You can then click on the View button to see that site's certificate. That may be an easier way for you to access the certificate information.

source: From internet.