Similar to the dedicated web hosting service, but the user owns the colo server; the hosting company provides physical space that the server takes up and takes care of the server. This is the most powerful and expensive type of web hosting service. In most cases, the colocation provider may provide little to no support directly for their client's machine, providing only the electrical, Internet access, and storage facilities for the server. In most cases for colo, the client would have his own administrator visit the data center on site to do any hardware upgrades or changes. Formerly, many colocation providers would accept any system configuration for hosting, even ones housed in desktop-style minitower cases, but most hosts now require rack mount enclosures and standard system configurations.
On the topic of dedicated hosting, many web hosting services also offer managed hosting. This type of hosting sees the web host act as your IT department, handling a server's maintenance and upkeep. This hosting option is something that you'd typically find with dedicated servers, so it's a business-centric addition. Naturally, it adds a few bucks to the hosting cost, but nothing that should break the bank if you have the resources for a dedicated server.