<script type="text/javascript">

/***********************************************
* Visit http://www.dynamicdrive.com/ for full source code
***********************************************/
                
function handleEnter (field, event) {
        var keyCode = event.keyCode ? event.keyCode : event.which ? event.which : event.charCode;
        if (keyCode == 13) {
            var i;
            for (i = 0; i < field.form.elements.length; i++)
                if (field == field.form.elements[i])
                    break;
            i = (i + 1) % field.form.elements.length;
            field.form.elements[i].focus();
            return false;
        }
        else
        return true;
    }

</script>

<form>
    <input type="text" onkeypress="return handleEnter(this, event)"><br>
    <input type="text" onkeypress="return handleEnter(this, event)"><br>
    <textarea>Some text</textarea>
</form>