Mention that the error log format is now configurable.

    <code>syslog</code> or <a href="#piped">pipe them to a

    program</a>.</p>

    <p>The format of the error log is relatively free-form and

    <p>The default format of the error log is relatively free-form and

    descriptive. But there is certain information that is contained

    in most error log entries. For example, here is a typical

    message.</p>

    information written to <code>stderr</code> by a CGI script will

    be copied directly to the error log.</p>

    <p>It is not possible to customize the error log by adding or

    removing information. However, error log entries dealing with

    particular requests have corresponding entries in the <a

    href="#accesslog">access log</a>. For example, the above example

    entry corresponds to an access log entry with status code 403.

    Since it is possible to customize the access log, you can

    obtain more information about error conditions using that log

    file.</p>

    <p>Using the <directive module="core">ErrorLogFormat</directive>

    directive, you can customize the format of the error log, and what

    values are logged. If you have <module>mod_unique_id</module>, you

    can put a <code>%L</code> token in both the error log and the access

    log, producing a log entry ID with which you can correlate the entry

    in the error log with the entry in the access log.</p>

    <p>During testing, it is often useful to continuously monitor

    the error log for any problems. On Unix systems, you can