Try this one:
<!doctype html>
<html>
<head>
<title>Calculator</title>
</head>
<body>
<table border="1px" width="75%">
<tr height="50px">
<td colspan="4">
<input type="text" style="width:95%;height:50px"/>
</td>
</tr>
<tr height="50px">
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
</table>
</body>
</html>
