If your Firefox give no respond when you click the Page Up, Page Down, Home or End button, you might have activated caret browsing. You might also notice that there will be a blinking text cursor when you click on a passage or text on a website.
You might have accidentally activated the caret browsing without [...]

Firefox by default is already very powerful internet browser, but you are probably not getting the most out of it. Getting the most out of Firefox basically means doing more on Firefox with less time. That will definitely increase your productivity.
Speed up Firefox
You have probably seen this else where as it has been posted millions [...]