<input onclick="clave('7', 'campo');" type="button" value="7" name="7" id="boton" style="height: 40px; width: 40px">
<input onclick="clave('8', 'campo');" type="button" value="8" name="8" id="boton" style="height: 40px; width: 40px">
<input onclick="clave('9', 'campo');" type="button" value="9" name="9" id="boton" style="height: 40px; width: 40px"><br>
<input onclick="clave('4', 'campo');" type="button" value="4" name="4" id="boton" style="height: 40px; width: 40px">
<input onclick="clave('5', 'campo');" type="button" value="5" name="5" id="boton" style="height: 40px; width: 40px">
<input onclick="clave('6', 'campo');" type="button" value="6" name="6" id="boton" style="height: 40px; width: 40px"><br>
<input onclick="clave('1', 'campo');" type="button" value="1" name="1" id="boton" style="height: 40px; width: 40px">
<input onclick="clave('2', 'campo');" type="button" value="2" name="2" id="boton" style="height: 40px; width: 40px">
<input onclick="clave('3', 'campo');" type="button" value="3" name="3" id="boton" style="height: 40px; width: 40px"><br>
<input onclick="clave('.', 'campo');" type="button" value="." name="." id="boton" style="height: 40px; width: 40px">
<input onclick="clave('0', 'campo');" type="button" value="0" name="0" id="boton0" style="height: 40px; width: 40px">
<input type="reset" value="DEL" name="DEL" id="boton" style="height: 40px; width: 40px">