the unique non-ambiguous order defined by the formal grammar
Syntax
Values
auto
The user agent will set the document's orientation automatically, typically based on the device's orientation as determined by an accelerometer (if the device has such a hardware sensor), although there is often a user-controlled, OS-level "Lock orientation" setting that will trump the accelerometer reading.
portrait
The document should be locked into portrait orientation.
landscape
The document should be locked into landscape orientation.