html-imenu-regexp

html-imenu-regexp is a variable defined in `sgml-mode.el'.
Its value is

"\\s-*]*>\\(<[^\n<>]*>\\)*\\s-*\\([^\n<>]*\\)"

Documentation:
A regular expression matching a head line to be added to the menu.
The first `match-string' should be a number from 1-9.
The second `match-string' matches extra tags and is ignored.
The third `match-string' will be the used in the menu.