Client denied by server config?

[Karabaja]

I keep getting this in error log. But not constantly but every now and then. And what is denied is just some gif images that are a part of vbulletin. Like new post icon or something like that. What could be the reason for that? Maybe someone visiting with a proxy. I tried few times with a proxy to open the page and sometimes images are not loaded. Could that be a cause of these error logs?

[jdMorgan]

It's likely that you, your server admin, or the vBulletin program has added code to the httpd.conf server configuration or to a .htaccess file to prevent image hotlinking from your site based on the HTTP Referrer sent with the request.

If so, then these error log entries indicate that someone has visited a page with an <img src=> link pointing to your site, and their browser has attempted to load the image from your server. Since the Referer header indicates the image being loaded on a page from another site (not yours), the server is denying access.

Jim

[Philosopher]

or possibly just the browser being used at that time is not sending the referer. This is getting more and more common and I've seen a few people using htaccess rules to block hotlinking that don't account for empty referers.