In emacs, backspace doesn't do its work

[jronald]

When using the emacs config in the Handbook, `backupspace` doesn't do its job, but start the help system.
I tried to add

(global-set-key [backspace] 'backward-delete-char)

at the end of the config file, but it doesn't work.
I also check the hook functions, but can't find the problem.
If delete the config file, it works.
So I want to know where does it be configured?
Thanks.

the config file can be found at:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/emacs.html