As said at https://support.mozilla.org/en-US/questions/968032, please don't use Firefox 10, it's not supported, bad for the web and you, and insecure. Locking this post as it's a duplicate of your last one. If you have specific reasons why Firefox 23 isn't good let us know and we can help you resolve them so that you can use the latest version of Firefox. You aren't going to find help on how to install such an old version of Firefox on this forum however.