This either means that the database information in your settings.php file is incorrect or we can't contact the PostgreSQL database server. This could mean your hosting provider's database server is down.
The PostgreSQL error was: pg_connect() [<a href='function.pg-connect'>function.pg-connect</a>]: Unable to connect to PostgreSQL server: FATAL: connection limit exceeded for non-superusers
Currently, the database is drupal, the username is pgsqluser, and the database server is db.planet-lab.org.
For more help, see the Installation and upgrading handbook. If you are unsure what these terms mean you should probably contact your hosting provider.