Form Designer: How to disable the Enter key in a web form

Form submission by pressing the ENTER key is standard HTML form behavior.

To disable this, click the gear icon in the Form Designer toolbar to open the Form configuration panel; then, on the Web References tab, add the following JavaScript code:

<script type="text/javascript">

function stopRKey(evt) { 
    var evt = (evt) ? evt : ((event) ? event : null);
    var node = (evt.target) ? evt.target : ((evt.srcElement) ? evt.srcElement : null);
    if ((evt.keyCode == 13) && (node.type=="text")) {
        return false;
    }
}

document.onkeypress = stopRKey;

</script>

Reference: http://webcheatsheet.com/javascript/disable_enter_key.php