Wikileaks principal host was on amazon.com servers. Amazon stopped hosting earlier this week. But Wikileaks had back-up servers including at Bahnhof one of Sweden's largest ISPs and a partner in São Tomé's national domain holder. Wikileaks used the firm everydns (http://www.everydns.com/) to provide DNS services (i.e. resolving web addresses to IP addresses).
I am in formed that everydns has stopped providing DNS services for them early Friday morning due to Denial-of-Service attacks and hence Wikileaks is offline.
I also noted this morning that the UK Guardian newspaper's Wikileaks blog was offline but seems to be back up now ...
I am assured that they will switch dns-provider.