/*
Always prefix your styles with a unique selector your widget has
to prevent your styles from affecting other elements of the same
selector pattern. In this case, only those under .stopwatch gets
affected.
*/
.stopwatch .controls {
    font-size: 12px;
}

/* I'd rather stick to CSS rather than JS for styling */

.stopwatch .controls button{
    padding: 5px 15px;
    background :#EEE;
    border: 3px solid #06C;
    border-radius: 5px
}

.stopwatch .time {
    font-size: 150%;
}