How does to error_page when this issue

[defage]

some url like:  http://localhost.com/%u
It will response http 400 status , and when generate this response
,nothing found  in error log or access log.

how to config this issue error_page?

my config
location / {
    error_page   400 =/400;
}

location /400 {
    root   /path/some/path;
}
it don't work.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,228031,228031#msg-228031