Betfair have announced the following:-
"Please be aware that there is a planned maintenance scheduled for Monday 23rd November 06:15 -10:15 (GMT) during which time the site will be unavailable.
The web site is being taken down to perform essential network upgrades.
For regular updates please visit our service information page at
http://service.betfair.info
We would like to apologise for any inconvenience this may cause and assure you that we will do our best to complete this upgrade as soon as we can."