10.6.8, latest Safari and Firefox, maybe others do it but those are the two I use.

When clicking on the Macte.ch Generate a short URL for this page: Get Link button at the bottom right of the pages here it throws up a warning Sorry, secure code you entered is not valid. Try again please.

After clicking OK in the warning box it does take you to the page to get the short url though.

I must admit that I had never tried it before today, so I don't know if it ever was working right.