Different buttons on IPAD and IPHONE

Hi,
I am using the code below into a few buttons (INPUT). They usually appear in various browsers, but the iPhone and iPad, the buttons are smaller in length and the color changed assuming degrades.

Where is the problem?

<input class="BTSALVAR" type="button" value="SALVAR" />

input.BTSALVAR {
padding: 20px 30px 20px 30px !important;
background-color: #83a846;
font-size: 20px !important;
-moz-border-radius: 3px;
-webkit-border-radius: 3px;
border-radius: 3px;
cursor: pointer;
color: #ffffff;
border: none  !important;
}

input.BTSALVAR:hover {
background-color: #8fb058;
}

input.BTSALVAR:focus {
outline: 0;
}

THANKS