Low This Hint is of the lowest significance, and should only be addressed if there are not more serious issues which have not been handled. Issue This Hint represents an error or problem that needs to be fixed.

Document compatibility mode in <head> and headers differ

This means that the URL in question has the document compatibility mode set in the <head> and the HTTP headers, and their values are different.

Why is this important?

Document compatibility determines how Internet Explorer renders your web page and how the JavaScript will work, and allows you to temporarily tell Internet Explorer to display a page or website in a document mode used by a previous version of the browser.

The document compatibility mode can be set in the <head> and in HTTP headers. If it is set in both places, yet their values are different, this could lead to the incorrect mode being used, because the <head> value will be ignored as the HTTP Header takes priority.

What does the Hint check?

This Hint will trigger for any internal HTML URL which has different values set for document compatibility in the <head> and the HTTP header.

Examples that trigger this Hint:

The Hint would trigger for this URL if it had both of the following;

Document compatibility set in the <head>:

<meta http-equiv="X-UA-Compatible" content="IE=8">

AND set in the HTTP Header, but to a different value:

HTTP/... 200 OK

X-UA-Compatible: IE=Edge

How do you resolve this issue?

Either ensure that the two values match, or change the setup so that the document compatibility mode is only set in one location.

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