Always use the cursor keys to navigate
within webpages allows you to move through web content as if
you were inside a read-only editor.
You can use the keyboard to select web content and copy it to the
clipboard. You can enable this feature by selecting Tools > OptionsEdit > PreferencesFirefox > Preferences,
opening the General tab in the Advanced panel,
and checking the Always use the cursor keys to navigate within webpages
optionpreference.