Echo authoring does not support the following HTML tags:
<link> <style> <script>
Using these HTML tags could compromise the security, design, and mobile-friendliness of Echo.
To use these tags in an activity without disrupting Echo, create the content outside of Echo as an HTML file and upload them as a PDF or HTML File attachment.
Echo is constantly being improved based on the feedback from users and we strive to keep our documentation up to date. If this document doesn’t match what you are seeing in Echo, please let us know.