LinuxQuestions.org - Letting a user logon without password

Hello. This is my first time writing in this forum.
I am looking for a solution in Apache web server. It should be possible for a user to log in without entering user name and password.
I saw en excellent web site called www.startssl.com. When I got configured there, I needed no password when logging in. My browser Firefox stores all certificates necessary. That server installed a certificate in my browser so that I am authenticated. All I had to do was to visit that web site where I was immediately logged in. That happens through mod_ssl in Apache.
I wonder how i do that with my own users at my web site. I plan to have a little web site with my blog with my opinions and I invite users to comment on my opinions. The users will need to log in through the simple method that I describe.
How can I make Apache use mod_ssl to do this?
Also, I can script the web server with PHP.