для bootstrap 4 (100% рабочий вариант):
a.active.focus,
a.active:focus,
a.focus,
a:active.focus,
a:active:focus,
a:focus,
button.active.focus,
button.active:focus,
button.focus,
button:active.focus,
button:active:focus,
button:focus,
.btn.active.focus,
.btn.active:focus,
.btn.focus,
.btn:active.focus,
.btn:active:focus,
.btn:focus {
outline: 0!important;
outline-color: transparent!important;
outline-width: 0!important;
outline-style: none!important;
box-shadow: 0 0 0 0 rgba(0,123,255,0)!important;
}
