Hi Antonio,
Postgres is very reliable and does support a type high availibility. It has several methods of replication that mean you can keep a slave database up to date with changes from your master.
The streaming replication is quite easy to set up and works extremely well. http://wiki.postgresql.org/wiki/Streaming_Replication
However, implementing failover (Automatic or not) if there is a problem is for the administrators of the database to do.