~/.w3m/mouse syntax:

menu <menu string - default empty>
lastline <lastline string - default "<=UpDn">
button <num> <pos> <func> [<arg>]

<num>:   1 : left button
         2 : middle button
         3 : right button

<pos>:	menu <x1> <x2>		: click on menu
	lastline <x1> <x2>	: click on last line
	default			: default action
	anchor			: click on anchor
	active			: click on active anchor
	tab			: click on tab

<x1>: left column pos 
<x2>: right column pos

menu in <pos> can be omited for backward compatibility.

default configuration (in func.c)


button	1 default	MOVE_MOUSE
button	2 default	BACK
button	3 default	MENU_MOUSE

button	1 active	GOTO_LINK

button	1 tab		TAB_MOUSE
button	2 tab		CLOSE_TAB_MOUSE

lastline	"<=UpDn"
button	1 lastline 0 1	BACK
button	1 lastline 2 3	PREV_PAGE
button	1 lastline 4 5	NEXT_PAGE

For example
 
- In ~/.w3m/mouse

   button 1 anchor COMMAND "MOVE_MOUSE; GOTO_LINK"

 you can jump to link by left click on non-active anchor.

- In ~/.w3m/menu

  menu Active
   func   "Display LInk       (a)"        GOTO_LINK       "a"
   func   "Open in new tag    (t)"        TAB_LINK        "t"
   func   "Save link          (d)"        SAVE_LINK       "d"
   func   "External browser   (m)"        EXTERN_LINK     "m"
  end

  and ~/.w3m/mouse

   button  3 anchor	MENU_MOUSE	Active

  then you can open menu by right click on anchor.