Mara allows for user-friendly handling of system error pages, such as 404 (missing page)
By default this is turned off, since it requires a small amount of configuration to tailor it to the specific site.
To activate custom error handling, open the .htaccess file in the base directory of your website. Use an FTP program and/or text editor to do this. The lines in question are:
# ErrorDocument 403 /.error.php?err=403&noadmin
# ErrorDocument 404 /.error.php?err=404&noadmin
You need to remove the # from each, to activate these lines. If your site is in the root of the webspace or you are using a subdomain, no further editing should be needed. If in a subdirectory of the webspace, you need to prefix that subdirectory to the path, eg:
ErrorDocument 404 /testsite/.error.php?err=404&noadmin
Be aware that the file is called .error.php -with a leading period.
With these correctly set, a missing page will result in a message within a proper site theme, complete with navigation menus. Thus, the visitor will not be 'dead-ended' if they attempt to access a page which has been deleted since they bookmarked it, but will instead be shown how to access other site pages.
A suggestion, why not add an amusing image to your .error.php file? This will alleviate what is often an aggravating situation for a site visitor by providing a spot of humour.