lucy24 - 8:54 am on Aug 11, 2012 (gmt 0)

You need to look at your error logs. Log level is out of your control, so you don't know how much or how little they will say. But they'll always give some information about 500-class errors.

Do you have a custom error page that's set with the ErrorDocument directive, or do you use the host's default filenames like "missing.html" or "forbidden.html"? I had a very belated "D'oh!" moment a few months ago as I realized that the config file must have a whole set of <Files> directives involving these specific names-- so if you use a different name you have to add conditions.

In particular, in rules that result in [F], like this

RewriteCond %{HTTP_REFERER} www\.example\.com [NC]
RewriteRule .* - [F]

you may need to put in a second Condition like

RewriteCond %{REQUEST_FILENAME} !my403\.html

to keep from going around in circles. I've copped out by putting a single Rule at the very beginning:

RewriteRule (boilerplate|pictures/(hotlink|smallgifs/onedot)) - [L]

That intercepts anything that has already been rewritten. It also gives a free pass to anyone asking for these files by name, so there are drawbacks. But in my case I don't think they could actually do anything with this group of files.