Important: #76166 - X-UA-Compatible not set in backend anymore ¶
See Issue #76166
As the official recommendation of Microsoft regarding the X-UA-Compatible tag is to not set this in the HTML code but instead via server configuration, the tag is not rendered by default in the backend anymore.
The TYPO3 default
files already contain the corresponding settings.
If you are using Internet Explorer configured to use compat mode by default, you may need to set these settings to ensure