For example add into /etc/apt/sources.lists following lines:

# some coment
deb http://www.cecak.cz/debian/squeeze ./

	Name	Last modified	Size	Description
	Parent Directory		-
	HEADER.html	10-Nov-2010 09:58	153
	Override	10-Nov-2010 09:55	0
	Packages	10-Nov-2010 09:55	7.1K
	Packages.gz	10-Nov-2010 09:55	1.4K
	php4/	21-Feb-2011 21:58	-
	postfix-cdb_2.7.1-1-loc1_i386.deb	10-Nov-2010 09:55	41K
	postfix-dev_2.7.1-1-loc1_all.deb	10-Nov-2010 09:55	143K
	postfix-doc_2.7.1-1-loc1_all.deb	10-Nov-2010 09:55	1.0M
	postfix-ldap_2.7.1-1-loc1_i386.deb	10-Nov-2010 09:55	48K
	postfix-mysql_2.7.1-1-loc1_i386.deb	10-Nov-2010 09:55	43K
	postfix-pcre_2.7.1-1-loc1_i386.deb	10-Nov-2010 09:55	43K
	postfix-pgsql_2.7.1-1-loc1_i386.deb	10-Nov-2010 09:55	43K
	postfix_2.7.1-1-loc1.dsc	10-Nov-2010 09:55	957
	postfix_2.7.1-1-loc1.tar.gz	10-Nov-2010 09:55	3.7M
	postfix_2.7.1-1-loc1_i386.changes	10-Nov-2010 09:55	3.5K
	postfix_2.7.1-1-loc1_i386.deb	10-Nov-2010 09:55	1.3M