statistics collector

I have completed installation of PostgreSQL (8.0.1) on Windows XP SP1.
I must say that I'm newbie in postgres world.
I've readed manual and changed conf file:

#---------------------------------------------------------------------------
# RUNTIME STATISTICS
#---------------------------------------------------------------------------

# - Statistics Monitoring -
log_statement_stats = true

stats_start_collector = true
stats_reset_on_server_start = true
stats_command_string = true
stats_row_level = true
stats_block_level = true

I have php script that read data from table.
The question is why I don't see any changes in statistics ? (both in
pgadmin and by quering for example "pg_statio_user_tables" )

I really need to know how many blocks where readed from disk. I was
looking into mysql but there is any feature that give this possibility.