Link: CSS-Tricks: Remove Gray Highlight When Tapping Links in Mobile Safari

This is a simple tricks but very useful if you’re trying to make a button in HTML looks like a real button in touch devices.

Remove the tap highlight:

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-webkit-tap-highlight-color: rgba(0,0,0,0);

and make the :active state works when user touches that element:

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document.addEventListener("touchstart", function(){}, true);