Netcraft released table list of most relable hosting company sites in May 2009. Most notable in this month’s rating that top list is headed by FreeBSD operating system.

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New York Internet, pair Networks and INetU had the most reliable hosting company sites in May 2009. Each of these sites responded resiliently to Netcraft’s performance collectors throughout the month, with not a single failed request.

The New York Internet’s got its second consecutive appearance at the top. Established in 1996, the company’s core services now include dedicated servers, colocation and virtual web hosting – all backed with a 99.999% uptime guarantee.
pair Networks also started off in 1996, with a $10,000 family loan funding a single employee and a partial T-1 line. The company has since grown to offer dedicated servers, virtual private servers and high volume hosting from its own datacentres in Pennsylvania, which use GigE connections to five diverse backbone networks.
INetU is an enterprise managed hosting company, also located in Pennsylvania. They stand by their network performance by offering a 100% uptime service level agreement. Managed services provided by INetU include MySQL and MS SQL database clusters, Exchange servers, virtualization and firewalls. Their clients include Fortune 500 companies such as Microsoft, Intel and Northrop Grumman.
Full table is available here