Seems to be working here.

Do you see the usual pop-up at the bottom of the Firefox window if you hover a link to show the link URL?

You can try basic steps like these in case of issues with web pages:

Reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Hold down the Shift key and left-click the Reload button
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

Clear the cache and the cookies from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

The first 4 links under "Register Yourself" do not work for me. Those are not standard links (the address is "#"); they rely on a script. Without spending a great deal of time parsing the site's scripts, I couldn't tell you why those "links" are not being activated.

Those four links aren't working in Google Chrome as well.
In the menu at the left there is also a "#" link that does have an onclick attribute to open a PDF file that works.