2.1.12 [HTML5:2014] Section 22.214.171.124 The dir attribute
V0021: The auto keyword is not supported
The specification states:
... The dir attribute The dir attribute specifies the element’s text directionality. The attribute is an enumerated attribute with the following keywords and states: ... The auto keyword, which maps to the auto state Indicates that the contents of the element are explicitly directionally isolated text, but that the direction is to be determined programmatically using the contents of the element (as described below).
All document modes (All versions)
auto keyword is not