The HTML5 specification has made this type of meta element obsolete in HTML, so you should not use it for pages written in HTML5. This is due to the widespread confusion surrounding the use of this construct. In addition, browsers are inconsistent in the way they handle this information.
Given this, it is strongly recommended that you not use this Content-Language meta element in any HTML format.
What to do
Remove the Content-Language meta element, and ensure that you have used an attribute on the html tag to specify the default language of the page.