Safari web inspector breaks media queries Using Safari Version 11.1, whenever I open the web inspector on a web page, all media queries in the CSS stop working. If I close the inspector, the problem goes away. This happens on any site.

Are other people experiencing this? Is there a setting that I've toggled?

Any help would be much appreciated! Thanks.
I also have experienced this problem. After doing some research I finally manage to solve the problem. 

Backup and remove ~/Library/WebKit/com.apple.Safari folder. 

A problem should disappear after that operation. Enjoy :D