If you like your notch, you can keep your notch: Apple's web design tips for the iPhone X
Nothing beats the official guidelines, though, and just one look at Apple's examples above can tell you where this thing is heading. Apple's WebKit team will include new code and development techniques tailored specifically for the iPhone X. Not everything is in the current version of its software tools for iOS 11, but a future update, likely around the iPhone X launch, will bring those up to speed.
For instance, there are new min and max commands which specify the navigation bars and to expand to the edges when the phone is held in portrait mode, but automatically prop larger inset margins in landscape for content, so that the notch on the side, the rounded corners, and the virtual nav bar at the bottom won't obscure the view. A picture is worth many words, so check out Apple's examples of dos and don'ts above.
source: Apple
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Things that are NOT allowed: