# in httpd.conf you need some lines like:

ErrorDocument 404 /custom_error/error_404_not_found.htm
[snip]
ErrorDocument 500 /custom_error/error_500_internal_server_error.htm

# then you need a custom doc where you specified it above, the guts of our 500 is .....

<div id="contentstart">
<h3>500 Internal Server Error</h3>
<p><img border="0" src="/images/thumbs_down.gif" width="14" height="17"> 
Sorry a 500 Internal Server Error error has occurred.</p>
<p>The server encountered an unexpected condition which prevented it from fulfilling 
the request. This is probably due to routine maintenance. Then again we may have to 
sack the programming team! This error has been logged and we will look into it, 
if it persists.</p>
<p>Sorry you have experienced a problem.</p>
<p>Click <a href="/index.htm">here</a> to return to our entry page, or 
<a href="/index/contact.htm">here</a> to contact us about the issue.</p>
<p><i>Kind Regards</i></p>
<p><i>The BlahBlah team</i>
</p><hr width="100%"><i>Apache 1.3.29 Server at blah.org Port 80</i>
</div>