Assertion: If a @charset declaration value has single, rather than double, quotes around it, the encoding declaration will not be recognised.

Notes:
The HTML page is served as UTF-8. The CSS stylesheet is in ISO 8859-15. For the test to be successful, the stylesheet has to be read as ISO 8859-15. The @charset rule is not correctly formed, so should be ignored, but the stylesheet should still be used.

If the box is blue, the stylesheet hasn't been read at all.