<script>

function displayResult(){

    document.getElementById("myHeader1").colSpan="2";

}

</script>

<table border="1">

    <tr>

        <th id="myHeader1">月份</th>

        <th id="myHeader2">存款</th>

    </tr>

    <tr>

        <td>January</td>

        <td>$100.00</td>

    </tr>

    <tr>

        <td>February</td>

        <td>$10.00</td>

    </tr>