Most ad blockers in use today rely on a list of filtering rules named EasyList. A likely erroneous rule was added for Speedtest.net which renders the site unusable by ad blocking users with EasyList enabled. This problem has since been resolved. To get Speedtest.net working again, do any of the following:

1. Manually force an update of your EasyList rules.

2. Add this custom rule in your ad blocker:  @@||speedtest.net/javascript/speedtest-main.js?*

3. Whitelist Speedtest.net to disable ad blocking on it.

4. Disable EasyList in your ad blocker.