Edit in JSFiddle

$('input[value="http://"]').on('change keydown', function() {
    $(this)[(this.value === 'http://' ? 'add' : 'remove') + 'Class']('placeholded')
}).change()

<input type=url placeholder=http://>
<input type=url value=http://>

input {
    display: block;
}

.placeholded {
    color: #aaa;
}

input:focus {
    color: #333;
}