PHP error happened

Technical information
Error type2
Error descriptionmysql_connect() [function.mysql-connect]: Unknown MySQL server host 'db51.perfora.net' (-2)
URLtosaconsultants.com/phpfiles/acronym_list.php?
Error file/homepages/34/d91385001/htdocs/tosa/phpfiles/include/dbconnection.php
Error line9
SQL query