[users@httpd] why "Service Temporarily Unavailable"

[aiyuanmin]

I use  ProxyPass / ajp://localhost:8009/ to combine tomcat and apache, 

Mapping  url   

 

RewriteRule ^/piece([0-9]+).htm$ /forum/view.jsp?id=$1 [PT]

 

Yes it work! But  sometimes  "Service Temporarily Unavailable" will appear
when I visit the url after mapping ,

Such as http://localhost/piece99.htm  , and if I vist
http://localhost/forum/view.jsp?id=99  , that'll never happen , who can tell
me why? 

Thanks a lot!