| # lang | |
| The `lang` prop on the `<html>` element must have a valid value based on ISO country and language codes. | |
| #### References | |
| 1. [axe-core, valid-lang](https://dequeuniversity.com/rules/axe/3.2/valid-lang) | |
| 2. [ISO Language Codes](http://www.w3schools.com/tags/ref_language_codes.asp) | |
| 3. [ISO Country Codes](http://www.w3schools.com/tags/ref_country_codes.asp) | |
| ## Rule details | |
| This rule takes no arguments. | |
| ### Succeed | |
| ```jsx | |
| <html lang="en"> | |
| <html lang="en-US"> | |
| ``` | |
| ### Fail | |
| ```jsx | |
| <html> | |
| <html lang="foo"> | |
| ``` |