A little irule which is helping me spotting errors while migrating configs to a10.
when HTTP\_REQUEST \{
set object "[HTTP::host][HTTP::path]"
\}
when HTTP\_RESPONSE \{
if \{
[HTTP::status] eq "404"
\} \{
log local0. "404: $\{object\}"
\#Just to be sure....
unset object
\}
\}