<html> element must have a lang attribute.
The interface language statement (lang attribute) allows user agents, in general, and assistive technologies, in particular, to parse and read the content more accurately. If a lang attribute is not specified or has an invalid value, the page language will fall back to the user agent or assistive technology's configured default language.
12<!DOCTYPE html>3<html lang="en">4 <!-- html content -->5</html>6
12<!DOCTYPE html>3<html lang="en">456 <!-- html content -->78 <p lang="fr">Bon Appétit</p>9</html>10
How Users Are Affected
Assistive technologies may misread or mispronounce the content and therefore mislead the user or even prevent him from understanding and using the interface properly.
WCAG Success criteria
This issue might cause elements to fail one or more of the following Success criteria:
3.1.1 Language of Page (A)