Security Alerts

All of sudden I'm getting the Security Alert pop-up for a web site where I
have to use a user name and password. I enter my user name and password and
click submit. Then I get the Security Alert below. I click OK but I can't
enter the site. I'm on the same web page where I have to enter my user name
and password again.
I guess I need to stop these popups because there is no redirect or whatever
that gets me onto the web site.

Here's the popup:
Security Alert: You are about to be redirected to a connection that is not
secure. The information you are sending to the current site might be
retransmitted to a nonsecure site. Do you wish to continue?