извините код немного не тот
<HTML>
<HEAD><TITLE></TITLE></HEAD>
<script language="JavaScript">
function plus()
{
rezultat.value=znah_1.value-(-1)*znah_2.value;
}
function minus()
{
rezultat.value=znah_1.value-znah_2.value;
}
function umn()
{
rezultat.value=znah_1.value*znah_2.value;
}
function del()
{
rezultat.value=znah_1.value/znah_2.value;
}
function rav()
{
}
</script>
<table border="2">
<tr>
<td>
<input id="znah_1" size="38">
</td>
<td rowspan="3" valign="top">
<input type="button" value=" + " onclick="plus()">
<input type="button" value=" - " onclick="minus()">
<input type="button" value=" * " onclick="umn()">
<input type="button" value=" / " onclick="del()">
<input type="button" value=" = " onclick="rav()"></td>
</tr>
<tr>
<td><input id="znah_2" size="38"></td>
</tr>
<tr>
<td><input id="rezultat" size="38"></td>
</tr>
</table>
</BODY>
</HTML>