Hos dejo aqui todo el codigo de la calculadora, haver si hos sirve.
ya funciona en todos los navegadores aunque el :active no me funciona en firefox no se si és normal.
aparte de eso solo falta el "=" en el enter y ya estaria.
Código HTML:
<html><head>
</head>
<style type="text/css">
#box {
margin: 40px auto;
width:196;
height:248;
color: inherit;
background: url("images/fondo.png");background-repeat: no-repeat; position:relative;}
img { border:0; }
.in {background:url(images/num.png); background-repeat: no-repeat;width: 127px; height: 40px;}
.zero {background:url(images/tot.png)0 -720px; top:191.667px; left:56.333px;}
.uno {background:url(images/tot.png)0 -675px; top:57.668px; left:13px;}
.dos {background:url(images/tot.png)0 -630px; top:57.668px; left:56.333px;}
.tres {background:url(images/tot.png)0 -585px; top:57.668px; left:99.666px;}
.cuatro {background:url(images/tot.png)0 -540px; top:102.334px; left: 13px;}
.cinco {background:url(images/tot.png)0 -495px; top:102.334px; left:56.333px;}
.seis {background:url(images/tot.png)0 -450px; top:102.334px; left:99.666px;}
.siete {background:url(images/tot.png)0 -405px; top:147px; left:13px;}
.ocho {background:url(images/tot.png)0 -360px; top:147px; left:56.333px;}
.nueve {background:url(images/tot.png)0 -315px; top:147px; left:99.666px;}
.logo {background:url(images/tot.png)0 0px; top:13.002px; left:142.999;}
.por {background:url(images/tot.png)0 -45px; top:147px; left:142.999px;}
.dividir{background:url(images/tot.png)0 -90px; top:191.667px; left:142.999px;}
.mas {background:url(images/tot.png)0 -135px; top:57.668px; left:142.999px;}
.menos {background:url(images/tot.png)0 -180px; top:102.334px; left:142.999px;}
.c {background:url(images/tot.png)0 -270px; top:191.667px; left:13px;}
.igual {background:url(images/tot.png)0 -225px; top:191.667px; left:99.666px;}
.zero:active {background:url(images/tot.png)-60px -720px; top:191.667px; left:56.333px;}
.uno:active {background:url(images/tot.png)-60px -675px; top:57.668px; left:13px;}
.dos:active {background:url(images/tot.png)-60px -630px; top:57.668px; left:56.333px;}
.tres:active {background:url(images/tot.png)-60px -585px; top:57.668px; left:99.666px;}
.cuatro:active {background:url(images/tot.png)-60px -540px; top:102.334px; left: 13px;}
.cinco:active {background:url(images/tot.png)-60px -495px; top:102.334px; left:56.333px;}
.seis:active {background:url(images/tot.png)-60px -450px; top:102.334px; left:99.666px;}
.siete:active {background:url(images/tot.png)-60px -405px; top:147px; left:13px;}
.ocho:active {background:url(images/tot.png)-60px -360px; top:147px; left:56.333px;}
.nueve:active {background:url(images/tot.png)-60px -315px; top:147px; left:99.666px;}
.logo:active {background:url(images/tot.png)-60px 0px; top:13.002px; left:142.999;}
.por:active {background:url(images/tot.png)-60px -45px; top:147px; left:142.999px;}
.dividir:active {background:url(images/tot.png)-60px -90px; top:191.667px; left:142.999px;}
.mas:active {background:url(images/tot.png)-60px -135px; top:57.668px; left:142.999px;}
.menos:active {background:url(images/tot.png)-60px -180px; top:102.334px; left:142.999px;}
.c:active {background:url(images/tot.png)-60px -270px; top:191.667px; left:13px;}
.igual:active {background:url(images/tot.png)-60px -225px; top:191.667px; left:99.666px;}
.zero,
.uno,
.dos,
.tres,
.cuatro,
.cinco,
.seis,
.siete,
.ocho,
.nueve,
.logo,
.por,
.dividir,
.mas,
.menos,
.c,
.igual {background-repeat: no-repeat; width: 40px; height: 40px;position: absolute;}
</style>
<body>
<div id="box">
<form name="Calc">
<input class="in" name="Input" type="text" style="font-family: arial; font-size: 15pt; text-align: left; position: absolute; top: 13.002px; left: 13px;">
<a class="logo" href="http://www.vicensvivesdigital.com" style="position: absolute; top: 13.002px; left: 142.999;"></a>
<a class="uno" name="one" value=" 1 " onclick="Calc.Input.value += '1'" type="button"></a>
<a class="dos" name="two" value=" 2 " onclick="Calc.Input.value += '2'" type="button"></a>
<a class="tres" name="three" value=" 3 " onclick="Calc.Input.value += '3'" type="button"></a>
<a class="mas" name="plus" value=" + " onclick="Calc.Input.value += '+'" type="button"></a>
<a class="cuatro" name="four" value=" 4 " onclick="Calc.Input.value += '4'" type="button"></a>
<a class="cinco" name="five" value=" 5 " onclick="Calc.Input.value += '5'" type="button"></a>
<a class="seis" name="six" value=" 6 " onclick="Calc.Input.value += '6'" type="button"></a>
<a class="menos" name="minus" value=" - " onclick="Calc.Input.value += '-'" type="button"></a>
<a class="siete" name="seven" value=" 7 " onclick="Calc.Input.value += '7'" type="button"></a>
<a class="ocho" name="eight" value=" 8 " onclick="Calc.Input.value += '8'" type="button"></a>
<a class="nueve" name="nine" value=" 9 " onclick="Calc.Input.value += '9'" type="button"></a>
<a class="por" name="times" value=" x " onclick="Calc.Input.value += '*'" type="button"></a>
<a class="c" name="clear" value=" c " onclick="Calc.Input.value = ''" type="button"></a>
<a class="zero" name="zero" value=" 0 " onclick="Calc.Input.value += '0'" type="button"></a>
<a class="igual" name="DoIt" value=" = " onclick="Calc.Input.value = eval(Calc.Input.value)"></a>
<a class="dividir" name="div" value=" / " onclick="Calc.Input.value += ' / '" type="button"></a>
</form>
</div>
</body></html>