Is it possible to set a default button for the ENTER key press for an entire webpage?

I googled and I came across the below code. But I'm not sure of what this line means `var keycode = (event.keyCode ? event.keyCode : (event.which ? event.which : event.charCode));` So I thought of posting this question here at stackoverflow.

Thanks.

```
<script language="javascript">
    $(document).ready(function () {
        $("input").bind("keydown", function (event) {
            var keycode = (event.keyCode ? event.keyCode : (event.which ? event.which : event.charCode));
            if (keycode == 13) {
                document.getElementById('btn').click();
                return false;
            } else {
                return true;
            }
        });
    });
</script>

```