This website embeds create-a-cookie.netlify.app (a different website), which attempts to store some data that could be used to track you across the web. However, Firefox isolates third-party site data by default.
The time you see when you navigate to create-a-cookie directly should be different from the time displayed below. In other words, if create-a-cookie had actually stored some personal information about you, it wouldn't be able to read or update it from this different website.
Click on the shield icon next to the address bar to toggle Enhanced Tracking Protection and see the difference it makes.
If you only see a white rectangle, you've changed your Firefox settings to block all third-party site data instead of just isolating it.
If you don't see anything, one of your extensions is blocking iframes.