The word SSL is an acronym which stands for Secure Socket Layer. It is a mode of communication between net clients; the browser that one uses to access the internet and the server on which the site is located. It happens to be not just any type of communication but an encrypted one. The encryption come in different types commonly known as bits. The good thing about this type of communication it allows a user to have a safe connection to a server therefore nobody may listen into it no matter how good they are at hacking. Take it like this in your office you have a personal assistant who directs important calls to you. They may listen into the conversation but the moment you press a special button their line goes dead.
An SSL connection can only exist in an environment that has conducive factors. That means an SSL connection may exist on a website but people can still listen in on the communication due to lack of factors that help the security of the communication. Many times has one landed on a site an a message appears on the toolbar of their net client. The message usually reads something like "This page contains both secure and nonsecure items." Or "Page contains unauthenticated content" This usually means that somewhere in the page's source there is an actual linking connection which may lead to another page. Something like "http://www.site.com" instead of using relative paths to lead where intended.
The purpose of an SSL is to secure communication therefore any page which is intended to appear under SSL connection should not have an actual connection to another page that is located in a different server.