Calculator in HTML , CSS

<html>
<head>
<title>Calculator</title>
<style>
input[type="button"]
{background-color:grey;
color:black;}
input[type="text"]
{background-color:grey;
border:solid black 2px;}
</style>
</head>
<body bgcolor="#F8F8FF">
<br/><br/><br/><br/><br/>
<form align="center">
<input type="text" size=20>
</form>
<table border="1" align="center" bgcolor="black">
<tr>
<td><input type="button" value="  1  "/></td>
<td><input type="button" value="  2  "/></td>
<td><input type="button" value="  3  "/></td>
<td><input type="button" value="  +  "/></td>
</tr>
<tr>
<td><input type="button" value="  4  "/></td>
<td><input type="button" value="  5  "/></td>
<td><input type="button" value="  6  "/></td>
<td><input type="button" value="  -  "/></td>
</tr>
<tr>
<td><input type="button" value="  7  "/></td>
<td><input type="button" value="  8  "/></td>
<td><input type="button" value="  9  "/></td>
<td><input type="button" value="  *  "/></td>
</tr>
<tr>
<td><input type="button" value="  =  "/></td>
<td><input type="button" value="  0  "/></td>
<td><input type="button" value="  C  "/></td>
<td><input type="button" value="  /  "/></td>
</tr>
</table>
</body>
</html>