Apache Reference: mod_log_referer, RefererIgnore

RefererIgnore

Exclude HTTP Referer Header Fields from Logging (Deprecated)
Syntax: RefererIgnore string [string ...]
Example: RefererIgnore www.foo.dom
Since: Apache 1.0

This directive adds to the list of strings that should be ignored in HTTP Referer header fields. If any of the string arguments in the list is contained in the Referer header field, then no referrer information will be logged for the request.