* chklinks does not support authentication yet.  W3C-LinkChecker
  have support on this.  As a workaround, You can use the syntax
  http://user:pass@some.where.com/some/path for Basic Authentication,
  but this does not work on Digest Authentication.  This practice is
  not encouraged, too.  Your password would be visable to anyone on
  this system using ps, including hidden intruders.  Also what you
  type in your shell will be saved to your shell history file.

* mailto: URLs should be supported by checking the validity of its
  DNS/MX record.

* Local file checking has only been tested on Unix and MSWin32.  More
  platforms should be tested, especially VMS and Mac.

* chklinks does not obey Crawl-delay: in robots.txt yet.  This is a
  problem in WWW::RobotRules, but not chklinks itself.
