Q: How do i get Shift-Tab to go backwards on a text terminal or XTerm?
aka: I hate the new text widgets, I can't go through the links with n and b
     I can go forward using TAB but how do i go backward on a terminal? 

A: Not all terminals can distinguish between a shiftted tab and an unshiftted
tab at all. Tab is indicated on a text terminal by a control-i. There is no
such thing as capital control characters, so if the terminal is going to
indicate a shift-tab somehow it has to be completely differently. The most
appropriate thing to use is probably "backtab" which on old text terminals was
sometimes a separate key and Emacs is already set up to recognize
automatically if it exists.

Making "backtab" work involves several steps. First you have to make sure your
console generates some character sequence to indicate the key you want to
generate a "backtab". Then you have to configure termcap or terminfo to
recognize that key sequence. Then you may have to make your programs do useful
things when they get a "backtab", Emacs for example will recognize it
automatically but except for the Widget and W3 commands nothing is ever bound
it it.

Step 1 On an XTerm: XTerm obeys standard X Toolkit translations which you can
use to specify what character sequence Shift-Tab generates. The following X
Resources will cause Shift-Tab and Meta-Shift-Tab to generate reasonable
character sequences. You can either put this in your .Xresources or .Xdefaults
file, or you can put it in /usr/lib/X11/app-defaults/XTerm to make it a
site-wide default. (On Debian systems you should put it in
/etc/X11/Xresources, not the app-defaults files):

XTerm*VT100.translations: #override \
   ~Meta Shift<Key>Tab: string(\033[Z) \n\
    Meta Shift<Key>Tab: string(\033\033[Z) \n

I recommend these sequences, they are based on what seems to be a more or less
standard sequence ^[[Z for backtab.

Step 1 On Rxvt: You can't, if you could you would use the keysym resource to
do something like this:

Rxvt*keysym.0xFF09: \033[Z

The problem is that as far as i can tell the keysym resource provides no way
to indicate modified keys like Shift-Tab or Meta-Tab.

Step 1 On A Linux Virtual Console: on a Linux virtual console you can
configure what character sequences are generated by which keys using the
loadkeys command. Many systems are set up to run loadkeys automatically on
startup with some keymap file. On Debian systems this is true, the keymap file
is specified in /etc/kbd/config and usually lives in the
/usr/lib/kbd/keytables directory. You want to put something like the following
in your keytable file:

keycode  15 = Tab   F91
	alt     keycode  15 = Meta_Tab        
	shift   alt     keycode  15 = F92

where keycode 15 is Tab on my keyboard (and probably any keyboard). This
defines Tab and Alt-Tab normally, and also defines Shift-Tab to be F91 and
Shift-Alt-Tab to be F92.

Then put something like this:
# backtab and M-backtab
string F91 = "\033[Z"
string F92 = "\033\033[Z"

later in the file. This defines what character sequence F91 (Shift-Tab) and
F92 (Alt-Shift-Tab) should generate. I recommend these sequences, they are
based on what seems to be a more or less standard sequence ^[[Z for backtab.

Step 2 On A Termcap System:

The termcap capability is kB, i'm not familiar with termcap tools, i think you
just need to add it to the /etc/termcap file for the terminal you're concerned
with as kB=\E[Z.

Step 2 On A Terminfo System:

The terminfo capability is kcbt (the long name is key_btab). You want to run
infocmp to generate an edittable copy of the terminal info. Add the
capability, then use tic to compile that information. Something like this:

infocmp $TERM > info
emacs info & # add kcbt=\E[Z, to the file
tic info

If you do this as root it should add the new definition to the system wide
terminfo database. If you do it as a normal user it should create a
~/.terminfo database with a local terminfo info definition for that terminal.

Step 3 On Emacs:

The standard terminal initialization should recognize the backtab capability
automatically. To test it try C-h c Shift-Tab and see what it calls the key.
To bind commands to it just use [backtab] in local-set-key or global-set-key
as in:

(local-set-key [backtab] 'hippie-expand)
or
(global-set-key [backtab] 'hippie-expand)

In the interest of maintaining a single consistent set of key bindings between
X and tty emacsen you may want to make equivalent X keystroke generate
"backtab" as well, you can do this by doing this:

(define-key function-key-map [S-tab] [backtab])
or
(define-key function-key-map [iso-lefttab] [backtab])

To make S-tab or whatever keystroke you made generate backtab on a terminal
be recognized as backtab under X11 as well. You can check how Emacs recognizes
this keystroke currently by doing C-h c <keystroke>.