2.1.86 [HTML5:2014] Section 220.127.116.11 Definitions
V0196: The setCustomValidity function is not supported
The specification states:
18.104.22.168 Definitions ... An element can have a custom validity error message defined. Initially, an element must have its custom validity error message set to the empty string. When its value is not the empty string, the element is suffering from a custom error. It can be set using the setCustomValidity() method. ...
IE9 Mode, IE8 Mode, IE7 Mode, and IE5 (Quirks) Mode (All versions)
is not supported.