+This is the default, but the option can be used to override an earlier
+.Fl f Ns Ar strict .
+.
+.It Fl f Ns Ar no-ign-escape
+Don't ignore invalid escape sequences.
+.
+.It Fl f Ns Ar no-ign-macro
+Do not ignore unknown macros at the start of input lines.
+.
+.It Fl f Ns Ar no-ign-chars
+Do not ignore disallowed characters.
+.
+.It Fl f Ns Ar strict
+Implies
+.Fl f Ns Ar no-ign-escape ,
+.Fl f Ns Ar no-ign-macro
+and
+.Fl f Ns Ar no-ign-chars .
+.
+.It Fl f Ns Ar ign-errors
+Don't halt when encountering parse errors. Useful with
+.Fl T Ns Ar lint
+over a large set of manuals passed on the command line.
+.El
+.
+.
+.Ss Output Options
+For the time being, only
+.Fl T Ns Ar html
+accepts output options:
+.Bl -tag -width Ds
+.It Fl O Ns Ar style=style.css
+The file
+.Ar style.css
+is used for an external style-sheet. This must be a valid absolute or
+relative URI.
+.It Fl O Ns Ar includes=fmt
+The string
+.Ar fmt ,
+for example,
+.Ar ../src/%I.html ,
+is used as a template for linked header files (usually via the
+.Sq \&In
+macro). Instances of
+.Sq \&%I
+are replaced with the include filename. The default is not to present a
+hyperlink.
+.It Fl O Ns Ar man=fmt
+The string
+.Ar fmt ,
+for example,
+.Ar ../html%S/%N.%S.html ,
+is used as a template for linked manuals (usually via the
+.Sq \&Xr
+macro). Instances of
+.Sq \&%N
+and
+.Sq %S
+are replaced with the linked manual's name and section, respectively.
+If no section is included, section 1 is assumed. The default is not to
+present a hyperlink.