FoxReplace is one of those underrated Firefox add-ons and if you don't want to install it for now because you might not need it today, you should definitely bookmark it because you will need it some time for sure. But let me tell you how it helped me.

We recently moved from webupd8.blogspot.com to www.webupd8.org and Google says that when doing that, you should replace all your internal links (links in posts included) from your old address to the new one. We had about 1800 posts to date so that's not an easy task. But FoxReplace can automatically search and replace strings upon opening a page, and this includes HTML too. So basically, all I had to do was click the edit button on posts and then re-publish them, without having to manually edit anything. Believe me, that was a real time-saver.