My buttons all have a highlight around them after I click them. This is in Chrome.
I've noticed the same and even though it really annoys me, I believe there is no proper way of handling this.
I would recommend against all the other solutions given because they kill the accessibility of the button completely, so now, when you tab to the button, you won't get the expected focus.
This should be avoided!
.btn:focus {
outline: none;
}