Simple Calculator

<html>
<head>
<title>Simple Calculator</title>
</head>
 <body>
 <form name="Calculator">
  <table>
    <tr>
      <td colspan="4">
        <input type="text" name="display" id="display" disabled>
      </td>
    </tr>
    <tr>
      <td> <input type="button" name="one" value="1" onclick="Calculator.display.value += '1'"> </td>
      <td> <input type="button" name="two" value="2" onclick="Calculator.display.value += '2'"> </td>
      <td> <input type="button" name="three" value="3" onclick="Calculator.display.value += '3'"> </td>
      <td> <input type="button" class="operator" name="plus" value="+" onclick="Calculator.display.value += '+'"> </td>
    </tr>
    <tr>
      <td> <input type="button" name="four" value="4" onclick="Calculator.display.value += '4'"> </td>
      <td> <input type="button" name="five" value="5" onclick="Calculator.display.value += '5'"> </td>
      <td> <input type="button" name="six" value="6" onclick="Calculator.display.value += '6'"> </td>
      <td> <input type="button" class="operator" name="minus" value="-" onclick="Calculator.display.value += '-'"> </td>
    </tr>
    <tr>
      <td> <input type="button" name="seven" value="7" onclick="Calculator.display.value += '7'"> </td>
      <td> <input type="button" name="eight" value="8" onclick="Calculator.display.value += '8'"> </td>
      <td> <input type="button" name="nine" value="9" onclick="Calculator.display.value += '9'"> </td>
      <td> <input type="button" class="operator" name="times" value="x" onclick="Calculator.display.value += '*'"> </td>
    </tr>
    <tr>
      <td> <input type="button" id="clear" name="clear" value="c" onclick="Calculator.display.value = ''"> </td>
      <td> <input type="button" name="zero" value="0" onclick="Calculator.display.value += '0'"> </td>
      <td> <input type="button" name="doit" value="=" onclick="Calculator.display.value = eval(Calculator.display.value)"> </td>
      <td> <input type="button" class="operator" name="div" value="/" onclick="Calculator.display.value += '/'"> </td>
    </tr>
  </table>
 </form>
 </body>
</html>