counts of groupings by date year-month

Hi,
I have a table called temp

access_date | active | status
-------------+--------+--------
2009-02-01 | t | 15
2009-02-01 | f | 16
2009-02-02 | f | 17
2009-02-01 | t | 17
2009-02-02 | f | 21
2009-01-01 | t | 20
2009-01-01 | t | 21
2009-01-01 | f | 21

What I want is to be able to get counts of active by year-month. So the
output would be like:

year_month | count
------------+-------
200901 | 3
200902 | 5

I tried something like
SELECT to_char(access_date, 'YYYYMM') as year_month, count(year_month)
FROM temp GROUP BY year_month ORDER BY year_month;

but I'm unable to execute this query because the column "year_month"
doesn't exist in temp table.

Is it possible to get counts by year_month?

Thanks for your help in advance,
CC