Renamed opening to survey_start and deadline to survey_end.
Symmetry seems to be both pleasing and helpful when understanding the code.
# Directions for web crawlers.
# See http://www.robotstxt.org/wc/norobots.html.
User-agent: HTTrack
User-agent: puf
User-agent: MSIECrawler
User-agent: Nutch
Disallow: /