All errors? I'm not sure what you mean by that, but the errors that will come up 99.9% of the time are:
401 - Authorization Required
403 - Forbidden
404 - Not Found
500 - Server Error (probably can't fix this with error.php :])
So, in the root directory, make a .htaccess with the following:
ErrorDocument 401 /error.php
ErrorDocument 403 /error.php
ErrorDocument 404 /error.php
ErrorDocument 500 /error.php
And everything should redirect there. Just make sure in httpd.conf you have AllowOverride FileInfo set. Hope that helps ๐
Chris King