For those that the Firefox extension doesn't work: is because the csfloat extension on here is the 5.11.0 and the actual one is the 5.14.0. Temporary you could use the Debugging feature of firefox to use the 5.14 version. Google "load temporary addon firefox manifest", download the "extension-v5.14.0-firefox.zip" from csfloat github (link on csfloat web) and follow the steps. this way doesn't updates the extension permanently, when you close the browser, the extension stays the same as before, maintaining the update from the firefox add-ons library when that happens.