'What is the best way to display a persistent notification until dismissed?

I have a webpage that is accessible from 1-4 computers per server. Every once in a while I need to display and alert or notification or something along those lines with a message "Recipe xfg has exceeded 50m3 please take a test sample as soon as possible"

This means that the operators need to take the sample that day, it's best if they don't forget to do it that day so I would like to make sure they have seen it, but it is not super urgent so it should not freeze their browser. So I need the notification to

  1. Stay on screen until the user presses a dismiss button

  2. Not obstruct too much of the page

  3. Stay visible when navigating between my pages

  4. Not freeze the other functions in the page

I have trouble finding an alert or notification that satisfies all of this.



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