Exceptions URL

http://plsql-tutorial.com/plsql-exception-handling.htm
http://download.oracle.com/docs/cd/B13789_01/appdev.101/b10807/07_errs.htm
http://ss64.com/oraplsql/exception.html
http://download.oracle.com/docs/cd/B10501_01/appdev.920/a96624/07_errs.htm
http://www.techonthenet.com/oracle/exceptions/