A firefox add-on that uses blocked.org.uk to see if the page you're on is blocked by content filters in the UK
Find your Firefox plugins folder. Help, Troubleshooting, Profile Directory, "extensions" folder.
Place the contents of this git repo in a folder called "check@block.org" in this "extensions" folder.
Restart Firefox.
It should ask you for permissions to install it.
Right click on your toolbar and click customise. There should be a "Blocked" option you can drag into your toolbar
Zip up the contents of this repo into a ".zip" file. Rename it "check@blocked.org.xpi".
Place this online and get another Firefox user to open the URL in FireFox.
On any webpage, click the Block button in the toolbar. A new window will open, showing you what blocked.org knows about this site.