If your web page displays an error, you can see the errors with the activating error logging in Oracle XE Web server.

It allows you to trace PL/SQL errors when you develop a web application.

You must first activate the log option with a PL/SQL command.

SQL> execute dbms_epg.set_global_attribute('log-level', 3)

The different log-levels are:

0 - LOG_EMERG
1 - LOG_ALERT
2 - LOG_CRIT
3 - LOG_ERR
4 - LOG_WARNING
5 - LOG_NOTICE
6 - LOG_INFO
7 - LOG_DEBUG

After you can see the file:
/usr/lib/oracle/xe/app/oracle/admin/XE/bdump/xe_s00?_????.trc or C:\oraclexe\app\oracle\admin\XE\bdump\ xe_s00?_????.trc

To see the last error, you must open the most recent file with xe_s00 in its name.