As with every web startup, Twitter had its early hiccups and throughout 2007 and 2008 users came to expect the occasional arrival of the Fail Whale. During 2007, there were nearly six full days of downtime as its data centre struggled to cope with some very fast growth.

When the site goes down these days, it's quite a big deal.

Pub quiz fact: The whale image was created by Yiying Lu as a greeting card for friends.