bootstrap-button-default.css

.btn {
    font-size: 14px;
    padding: 6px 12px;
    margin-bottom: 0;

    display: inline-block;
    text-decoration: none;
    text-align: center;
    white-space: nowrap;
    vertical-align: middle;
    -ms-touch-action: manipulation;
    touch-action: manipulation;
    cursor: pointer;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    background-image: none;
    border: 1px solid transparent;
}
.btn:focus,
.btn:active:focus {
    outline: thin dotted;
    outline: 5px auto -webkit-focus-ring-color;
    outline-offset: -2px;
}
.btn:hover,
.btn:focus {
    color: #333;
    text-decoration: none;
}
.btn:active {
    background-image: none;
    outline: 0;
    -webkit-box-shadow: inset 0 3px 5px rgba(0, 0, 0, .125);
    box-shadow: inset 0 3px 5px rgba(0, 0, 0, .125);
}

/* default
---------------------------- */
.btn-default {
    color: #333;
    background-color: #fff;
    border-color: #ccc;
}
.btn-default:focus {
    color: #333;
    background-color: #e6e6e6;
    border-color: #8c8c8c;
}
.btn-default:hover {
    color: #333;
    background-color: #e6e6e6;
    border-color: #adadad;
}
.btn-default:active {
    color: #333;
    background-color: #e6e6e6;
    border-color: #adadad;
}

bootstrap-button-default.html

<a href="#" class="btn btn-default">button</a>

nice gist; but I think there should also be a border-radius of 4px to .btn class :)