<div class="input">
    <input type="button" id="btn" class="btn_mfyzm" value="免费获取验证码" />
   <script type="text/javascript">
var wait=5;
document.getElementById("btn").disabled = false;  
function time(o) {
        if (wait == 0) {
            o.removeAttribute("disabled");          
            o.value="免费获取验证码";
            wait = 5;
        } else {
            o.setAttribute("disabled", true);
            o.value="重新发送(" + wait + ")";
            wait--;
            setTimeout(function() {
                time(o)
            },
            1000)
        }
    }
document.getElementById("btn").onclick=function(){time(this);}
</script>
</div> 

 <li><span class="txt_name">验证码：</span><span class="code"  onclick="getVerify();" id="timeb1" style="cursor:pointer">免费获取验证码</span><input class="input_code" autocomplete="off" onblur="if(this.value=='') this.value='';" onfocus="if(this.value=='') this.value='';" value="" type="text"  name="verifyCode"  id="verifyCode" ></li>

function f_timeout(){
 
 $('#timeb1').html('<span id="timeb2">60</span>秒后重新获取');
 $('#timeb1').click(function(){});
 timer = self.setInterval(addsec,1000);

}

function addsec(){
 
 var t = $('#timeb2').html();
 //alert(t);
 if(t > 0){
  
  $('#timeb2').html(t-1);
  //alert(t);
 }else{
  
  window.clearInterval(timer);
  $('#timeb1').html('<span id="timeb2"></span>重新获取验证码');
  $('#timeb1').click(function(){getVerify();});
 }
 
}