Web-based applications and desktops

Ajax has prompted the development of websites that mimic desktop applications, such as word processing, the spreadsheet, and slide-show presentation. In 2006 Google, Inc. acquired one of the best-known sites of this broad class, Writely.[32] WYSIWYG wiki and blogging sites replicate many features of PC authoring applications.
Several browser-based "operating systems" have emerged, including EyeOS[33] and YouOS.[34] Although coined as such, many of these services function less like a traditional operating system and more as an application platform. They mimic the user experience of desktop operating-systems, offering features and applications similar to a PC environment, and are able to run within any modern browser. However, these operating systems do not directly control the hardware on the client's computer.

Source:http://en.wikipedia.org/wiki/Web_2.0