Web pages load slowly

A list of problems that cause(d) web pages on my servers to load slowly, and, if available, their solutions.

SESSION variables

A couple months ago, I noticed that my "authenticated" pages loaded more slowly, or not at all, compared to the public pages at http://energyteachers.org . Today, I was programming a page to get information through the server from a previous page, and I discovered the problem was related to session variables.

Now I know to use session_save_path() before declaring a session in PHP so that session variables are stored in my own folder instead of the same folder the hundreds of other sites on my shared server use.