Can I use CSS3 media query in HTML editors?
HTML Editor, Answers, Mailings, Message Templates
Basic CSS media type such as '@media screen' can be used in HTML editor regardless. You may see some mixed results with more advanced media queries such as seeing the string change to @media Unknown or code completely removed. This is the result of the Tidy utility that runs to clean up code. In order to avoid Tidy from making changes and to use the more advanced media queries, you will need to leave your editor on the source tab when you save and close. If you switch to the design tab, you will need to navigate back to the source tab and type in your query again.