인증 코드, 새로고침 실패

Question

<div class="formControls col-xs-8 col-xs-offset-3">    <input name="captcha" class="input-text size-L" type="text" placeholder="验证码" onblur="if(this.value==''){this.value='验证码:'}" onclick="if(this.value=='验证码:'){this.value='';}" value="" style="width:150px;">    <img src="{:captcha_src()}" id="captcha_img">    <a id="kanbuq" href="javascript:captcha_refresh();">看不清，换一张</a></div>

<script>    function captcha_refresh(){        var str = Date.parse(new Date())/1000;        $("#captcha_img").attr("src" , "/captcha?id="+str);    }</script>