Google has been changing the code used to display their search results a number of times over the past couple days. We recently updated SEO for Firefox and Rank Checker. Both should work as of now, and if any more SERP changes happen we will try to update the extensions as soon as possible.

If you need to update these tools you can do so within the Firefox browser by clicking on Tools in the top Firefox menu, then from the Tools menu click on Add-ons. This will pop up the Add-ons / extensions window. At the bottom of this window there is a Find Updates button you can click. That will bring in the new updates and then when you re-start the browser the extensions should be fully functional again.