<input type="text" onfocus="changeTip(this);" id="passText" name="passText" value="请输入密码"/>
<input style="display: none;" type="password" onblur="changeTip(this);" id="pass" placeholder="" name="pass" value=""/>
<script type="text/javascript">
function changeTip(th){
 var passText = document.getElementById('passText');
 var pass = document.getElementById('pass');
 if(th.id == 'pass'){
  if(th.value == '' || th.value.length == 0 ){
   passText.style.display='';
   pass.style.display='none';
  }
 }else{
  passText.style.display='none';
  pass.style.display='';
  pass.focus();
 }
}
</script>