Backports instruction does not work, why

[T <mlist4suntong@yahoo.com>]

Hi, 

I've been following the "Debian Backports - Instructions"
at http://www.backports.org/instructions.html
to use backports. However, it doesn't work for me:

I've done all the settings required in the instruction:

	$ grep backports /etc/apt/sources.list
	# backports
	deb http://www.backports.org/debian/ sarge-backports main

	$ grep -1 backports /etc/apt/preferences
	Package: *
	Pin: release a=sarge-backports
	Pin-Priority: 200

I want to install the backports' asciidoc.

	$ apt-cache policy asciidoc
	asciidoc:
	Installed: (none)
	Candidate: 6.0.3-1
	Version Table:
	7.0.2-4 0
	80 http://debian.yorku.ca testing/main Packages
	40 http://debian.yorku.ca unstable/main Packages
	7.0.2-3bpo1 0
	200 http://www.backports.org sarge-backports/main Packages
	*** 6.0.3-1 0
	1001 http://debian.yorku.ca sarge/main Packages
	100 /var/lib/dpkg/status

However, when I issued the apt-get as instructed, only the mail sarge
version is installed:

	$ apt-get -t sarge-backports install asciidoc
	[...]
	The following NEW packages will be installed:
	asciidoc python2.4
	[...]
	Setting up asciidoc (6.0.3-1) ...

	$ apt-cache policy asciidoc
	asciidoc:
	Installed: 6.0.3-1
	Candidate: 6.0.3-1
	Version Table:
	7.0.2-4 0
	80 http://debian.yorku.ca testing/main Packages
	40 http://debian.yorku.ca unstable/main Packages
	7.0.2-3bpo1 0
	200 http://www.backports.org sarge-backports/main Packages
	*** 6.0.3-1 0
	1001 http://debian.yorku.ca sarge/main Packages
	100 /var/lib/dpkg/status

Why is that? 

How can I install backports packages properly? I want to, as recommended, to
pick out single backports which fits my needs, and not to use all
backports available.