20. The non-transitory computer program product of claim 19 , wherein the process further comprises: identifying a media-dependent style rule encoded in the set of presentation semantics associated with the structured document; determining that the display requirement of the second type of media device satisfies the media-dependent style rule; and in response to the determination, deleting the media-dependent style rule from the set of presentation semantics and preserving the corresponding style property; wherein the style property corresponds to the satisfied media-dependent style rule.
19. A non-transitory computer program product encoded with instructions that when executed by one or more processors cause a process to be carried out for simulating a structured document as it would appear on different types of media devices, the process comprising: receiving, via a user interface, a user request to render, in a web browser executing on a first type of media device, a structured document in a layout specific to a second type of media device having a different display requirement than the first type of media device, the second type of media device being selected from a plurality of predefined types of media devices; determining a visual layout of a browser presentation of the structured document in accordance with a style property encoded in a set of presentation semantics associated with and specific to the second type of media device; and sending the laid out structured document including the style property specific to the second type of media device to the web browser for rendering on the first type of media device.