Mashups mix content from multiple sources by using feeds from public APIs. An example is an application that mashes information from a real estate company's Web site with a Web mapping interface from another site to show the location of area home listings. Mashing is a presentation layer approach to integration and composite applications that leverage Web technologies on both the consumer side (the browser) and the source side (Web feed protocols). Opportunistic applications are end-user-created composites based on an individual's need or context.