2.1.127 [HTML5:2014] Section 7.6.1 Making document regions editable: The contenteditable content attribute

V0299: An invalid value for the contentEditable attribute throws an "Invalid Argument" exception.

The specification states:

 ... Making document regions editable: The contenteditable content attribute
     ...
     The contentEditable IDL attribute, on getting, must return the string "true" if the 
     content attribute is set to the true state, "false" if the content attribute is set 
     to the false state, and "inherit" otherwise. On setting, if the new value is an ASCII 
     case-insensitive match for the string "inherit" then the content attribute must be 
     removed, if the new value is an ASCII case-insensitive match for the string "true" 
     then the content attribute must be set to the string "true", if the new value is an 
     ASCII case-insensitive match for the string "false" then the content attribute must 
     be set to the string "false", and otherwise the attribute setter must throw a 
     ["SyntaxError" DOMException/SyntaxError exception].

All document modes (All versions)

An invalid value for the contentEditable attribute throws an "Invalid Argument" exception.

V0298: The contentEditable attribute does not return inherit when its value is set to the empty string

The specification states:

 ... Making document regions editable: The contenteditable content attribute
     ...
     The contenteditable ... attribute is an enumerated attribute whose keywords are the 
     empty string, true, and false. The empty string and the true keyword map to the true 
     state. The false keyword maps to the false state. In addition, there is a third 
     state, the inherit state, which is the missing value default (and the invalid value 
     default).

All document modes (All versions)

The contentEditable attribute does not return inherit when its value is set to the empty string.