Tfl's useful Journey Planner at
http://journeyplanner.tfl.gov.uk/user/XSLT_TRIP_REQUEST2?language=en
has a new mechanism for delivering rather pretty adverts.

To get such adverts, Windows users should NOT have a line like the
following in
c:\windows\system32\drivers\etc\hosts
127.0.0.1 www.googletagservices.com # journeyplanner ads


Changes to hosts are picked up immediately in Internet Explorer and
after a reboot in Firefox.

http://en.wikipedia.org/wiki/Hosts_%28file%29 describes hosts.
YMMV
--
Walter Briscoe