The original UNIX terminals does not have the eight movement keys:
Up, Down, Left, Right, Top(HOME), Bottom(END), Page-UP, Page-DOWN.
Today there are still such keyboard in use for its compact size and touch-type efficiency, e.g. Happy Hacking keyboard, Das Keyboard and KBC POKER (KBC POKER II too). Even if you do not use one of these keyboard, you may still wish to use Linux without using these eight movement keys, to avoid moving fingers from touch-key positions during editing.
The EMACS cursor movement shortcut keys
EMACS keybinding supports the following movement keys:
Single character movement:
Ctrl+b/f/p/n: Left, Right, Up, Down
Alt+b/f: Move left a word/ Move right a word
Ctrl+h/d: delete the charater to the left/ delete the character to the right.
Ctrl+a/e: move to the begining (HOME)/ move to the end(END)
It is easy to get by without 8 keys on console. Emacs mode is supposed by readline(3), thus by bash, mysql, python and many others also already support them without any special configuration.
readline in addition supports Ctrl+u, which deletes from the current cursor position to the begining of paragraph. This combination does nothing on its own in Emacs, and it simply delete the whole line in gtk's EMACS keybinding mode, irregarding to the current cursor position.
By enabling GTK key bindings, these key-bindings would work on all GTK applications. This include Firefox.
Firefox would use EMACS keybindings if gtk is configured so. Many EMACS keybindings conflict with existing Firefox keybindings. Since emacs movement keybindings are used more frequently, we should make sure they take priority.
Some keys already do, like Ctrl+w would be taken as "delete previous word" in an HTML TEXTAREA, and it would be taken as "Close current tab" if the user is not editing text in an TEXTAREA.
Some keys are not.
Alt+d, meaning "deleting the current word from the cursor", would activate addressbar in Firefox, like Ctrl+L or F6 does. Remapping this keybinding requires an addon extension. The most popular keybinding editor addon for Firefox, "Customizable Shortcuts", does not offer remapping of Alt+d, instead, Keyconfig  do.
In emacs mode, the up-arrow and down-arrow replacements are Ctrl+p, in Firefox meaning "print the current page", and Ctrl+n, "Open the new browser window". They both can be disabled with Keyconfig mentioned above. A better solution is to make these keys cursor movement keys if the user is editing text, and browser function keys otherwise, like how Ctrl+w was treated. However such a solution has not been made possible yet.
All emacs-style shortcut keys defined in gtk's EMACS mode are usable in Chromium, if user is editing text; and in other cases, these shortcut keys function as browser shortcut keys. For example, Ctrl+p moves cursor one line up during editing, and in other occassions calls up "print webpage" dialogue.
xTerm by default ignores alt key. Alt key (or meta key) is not needed for the emacs-style replacements for the 8 cursor-keys, but are used in emacs-style cursor movement shortcuts, like word-delete.
Alt key is essentially ESCAPE key. Alt-something emits Escape key followed by that something. To enable alt-keys in xTerm put the following in ~/.Xresources:
gnome-terminal by default use alt-key to activate menu items. To let alt key emit Escape sequence, as console application would expect, go to Edit > Keyboard Shortcuts..., and uncheck "Enable menu access keys".