http://en.wikipedia.org/wiki/Zero_Footprint_Applications
Zero Footprint Applications (ZFAs, also called Zero Footprint Clients or Zero Footprint Software) refers to computer applications which do not require end users to install any software. Examples include most web based applications such as Webmail. The term is often used for a new generation of mobile device applications which run entirely embedded within the existing application framework of the device, such as a web browser, Java (programming language) or a combination of the two.