How do I drop a column from a table?

Hi,

I'm still quite new at this but it should be a simple operation:  How do I
drop a column form a Postgres table.  The next best thing would be knowing
how to change a column so that it can accept null values.

Any takers?

Thanks

Robert Carbonari
Programmer
Optimal Robotics Corp.
e-mail: robertc@optimal-robotics.com
phone:  (514)738-8885 ext. 146