Question : How to use SSL

I know this is basic but I want to clarify the use of SSL to satisfy my on curiousity.

Programitically how do you use SSL.  I know about certificates and such but how does a page know that it is supposed to use the HTTPS protocol?

What prevents a user from fliping back and forth from HTTPS to HTTP?

Answer : How to use SSL

It's been a while since I've done this (someone else does the web management now), but I recall being able to segregate pages (files and directories) based on criteria that I specify.  That is, I could specify a certain directory subtree as accessible under some conditions (such as https) and not others (such as http).  There were many possibilities and conditions.  However, I offer this suggestion as something to look into and try.  It's what you really want when you ask "Is there a way to make sure that in the previous example the index.html page is always accessed through HTTPS?  What if they are on the same server?"