Improve Firefox functionality with Dark Reader /dark-mode add-on extension.
This is a great free extension , you do not need to be loggedin to use it.
Using Dark-reader extension at all times (win7sp1 x64, 43in 4k monitor).
For Firefox each transit to a different web site the monitor screen flickers full-white, with max intensity , twice.
"This is bad for the eyes" to paraphrase Zaphod / in the parking lot at the Restaurant at the End of the Universe, The Hitchhiker's Guide to the Galaxy by Douglas Adams.
Thanks