Move the id that relates to each button into the button itself and read it using "this" which represents the button that fired the event
<form id="form1" runat="server">
<input type="button" class="content-button" value="One" data-id="1" />
<input type="button" class="content-button" value="Two" data-id="2" />
</form>
<script>
$(document).ready(function () {
$(".content-button").click(function (e) {
e.preventDefault();
var postId = $(this).data('id');
alert(postId);
});
});
</script>