重点看标红的
<input type="text" style="display:none" disabled autocomplete = "off" value=" ">
<input name="用户名" type="text" id="username" autocomplete="off"/><i>用户名</i>
<input type="password" style="display:none" disabled autocomplete = "off" value=" ">
<input name="密码" type="text" οnfοcus="this.type='password'" id="userpwd" autocomplete="off" /><i>密码</i>
或者 <input name="密码" type="password" readonly οnfοcus="this.removeAttribute('readonly');" id="userpwd" autocomplete="off" /><i>密码</i>
在文档加载完成后将用户名、密码输入内框设置为容空
window.load=function(){document.getElementById('密码域ID').value='';};
或者
document.getElementById('username').value='';
document.getElementById('userpwd').value='';