Text links, png buttons – everything has a grey background when you tap it on mobile webkit browsers. While this can server some usability functions, sometimes it’s just getting on your way. Lets say you have a fancy shaped button with some transparency. There will be grey background in the transparent area, whenever the user taps on that button and that definitely would look ugly.
The solution is as simple as adding: -webkit-tap-highlight-color: rgba(0,0,0,0); to your buttons, links or everything if you want.