* host checking: Host Checking.
* host lookup: Host Checking.
* http password: HTTP Options.
+* http referer: HTTP Options.
* http time-stamping: HTTP Time-Stamping Internals.
* http user: HTTP Options.
* ignore length: HTTP Options.
* recursion: Recursive Retrieval.
* recursive retrieval: Recursive Retrieval.
* redirecting output: Guru Usage.
+* referer, http: HTTP Options.
* reject directories: Directory-Based Limits.
* reject suffixes: Types of Files.
* reject wildcards: Types of Files.