Hello... An internal file in each add-on indicates the range of Firefox versions with which the extension is compatible. In the '''Firefox Add-ons''' area of Mozilla, you can review version compatibility information on the page for each available extension. If your installed version of Firefox does not fit within that range, installing the add-on results in an error, indicating that the add-on is not compatible. If your version of Firefox is incompatible with the add-on, you can: * Update to the latest version of Firefox. For more information, see [[Update Firefox to the latest release]] . * Find a version of the add-on that is compatible with your version of Firefox. The '''Firefox Add-ons'''website usually has the most up to date version of each add-on. * Use a different extension. For many extensions, there are similar extensions that provide the same functionality. For more information, see '''Firefox Add-ons'''. * Contact the author of the add-on at the support site listed on its add-on page. (Note: posting a review is not effective and will not reach the author.)