Galaxy Note 3 - Brightness Changes While Viewing Internet Pages

[m5james]

It's a built-in safety feature. You can have all the settings off, and it will still do it. What happens is when the temp of the phone goes above 90F the phone will automatically dim the screen to help cool things off. Once it's cool enough the brightness will go back up. There's nothing you can do about it. It's a Samsung thing.

This is the most logical answer. I unchecked everything as needed and it was still doing it. I noticed a little comment under the brightness slider saying adjustment is limited due to device temperature. Time for me to buy a thinner case.