So using the developer website in Safari....produces this.
How?
How is this even possible? I know.... they used Chrome to test and develop with... ;)
I am on the latest Safari. Sad.
Developer Website Navigation
Probably some extension you have installed.
No, this is css related.
It does blur the background when you hover over a menu. But the menu itself isn't blurred like it is in your screenshot.
Apple has like 58 million developers. Are they all seeing blurry pages and not saying anything? Am I the only one who sees is correctly? Or are you the only one who sees it wrongly?