回车键换行

<script type="text/javascript">                
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>