Hello,
Thank you for writing to Microsoft Community Forums.
I understand that you want to remove the Wireless Projection Banner from the screen as it keeps popping when you open a browser. May I know, if the PC is still connected to the wireless display when you are using the PC?
Also, you can try clicking on the PIN icon next to the Settings icon on the banner to unpin it.
However, as per the section Wireless projection experience in the article what's new in Windows 10, version 1809, the banner is designed similar to remote desktop connection where it will be removed when the wireless display is disconnected.
Hope it helps.
Regards,
Prakhar Khare
Microsoft Community – Moderator