How do I prevent updates on an entire table (but allow inserts) in Mysql 5.5? I want to make the rows in a Mysql table immutable, once they are inserted I don't want it to be possible to change them.  How can I do this?  

This question handles making individual rows immutable, but I'm hoping there is a better way to make all rows in a table immutable (ideally returning a suitable error message if any change is attempted).
You can revoke 'UPDATE' privilege for a particular table. Or you can write BEFORE UPDATE trigger that raises an error (using signals or issuing a statement that always fails).