jsp:页面

<label>验证码</label>

          <input type="text" class="text" style="width:150px;" id="txt_val" placeholder="验证码" name="txt_val" tabindex="3" οnkeypress="keyPress(this)"/>

js:

function onkeypress(obj){

  var theEvent = window.event || arguments.callee.caller.arguments[0];

  var code = theEvent.keyCode || theEvent.which;   if(code == 13){ //回车键的code等于13       $form("Xxx").submit();//提交表单   }

}