Thanks to add the support of the "content-type" field in the HTTP/S header in the "Webpage speed browser" monitor like "website" monitor
see the issue 686912 for more details
Thank you for writing to us.
We are in progress of upgrading the browser version and we planned to support after the upgrade. We will update this thread once we start working on the same.
- Rajeshwaran, Site24x7 Team.