In another thread, it was mentioned that Facebook has been modifying the site and no longer works in many older versions of Firefox. I think the newest version of Firefox for OSX 10.5 is Firefox 16. I don't know whether that version still works with FB or not.

That could be the problem, but you might also try the common troubleshooting steps such as:

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Bypass Firefox's Cache

You can clear Firefox's cache completely using:

"3-bar" menu button (or Tools menu) > Options > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"

In the dialog that opens, you can remove the site's cookies individually.

Then try reloading the page. Does that help?

On Mac use Firefox > Preferences instead of Tools > Options that is used on Windows.