The warning messages have now gone and the site is operating o.k., along with the one suggested by Trim.
However, I have tried another test site which I really like because, it not only gives up and down Broadband speeds, it also provides street maps(similar to Google's) so that you can see speeds in the area for one's own and other providers; and also trace routes right back to the telephone exchange and establish the average speeds emanating from the exchange.
http://top10.com/broadband/speedtest/
Ron.