plpgsql function docs

I've been searching google for most of the morning trying to find docs on
plpgsql functions, but haven't had much luck. Can someone point me in the
right direction?

What I need to do is delete all the records in tableA that has and id that's
not listed in tableB. well actually i want it to insert it to another table
then delete, but I just need some pointers on how to find the records that
aren't in the table.

Ok if you want to know why i want to do this, it is because the literacy
project i am working for has many different sites, and at best the sites
have a dialup connection. I want it so that the data is stored locally until
they click the upload button, at which time the data is uploaded. the
problem is if they delete a record it won't be deleted on my end since it
only uploads the new data. Therefore i want the clients to send a list of
all the id's and then check for ones that aren't there, and therefore
must've been deleted.

Well anyway that is the situation i'm in. All I need is a pointer to the
docs that will tell me how to do this, but I can't find it. Thanks for your
help.

Andrew