css中div盒子无法下移

css中盒子下移出现问题，无法下移

*{
    margin: 0px;
    padding: 0px;
    list-style-type: none;
}
.nav{
    position: 20px 30px;
    margin-bottom: 10px;
    padding-left: 15px;
    line-height: 43px;
    font-size: 18px;
}
.nav h1 a{
    margin-left: 10px;
    color:red ;
    text-decoration: none;
}
.nav h1 li a{
    text-decoration: none;
    color:black;
    font-family:\9ED1\4F53 ;
    font-size: 20px;
    width: 460px;
    position: relative;
    line-height: 30px;
    margin-left: 10px;
}

是要滚动向下时 盒子保持位置吗？


<html>
<body>
<div style="height:3000px;">1</div>
<div class="nav">
<h1>
    <li>
        <a>是让它保持位置吗？</a>
    </li>
</h1>
 </div>
</body>
</html>
<style>
*{
    margin: 0px;
    padding: 0px;
    list-style-type: none;
}
.nav{
    position: fixed;
    top:50px;
    margin-bottom: 10px;
    padding-left: 15px;
    line-height: 43px;
    font-size: 18px;
    border:1px solid green;
}
.nav h1 a{
    margin-left: 10px;
    color:red ;
    text-decoration: none;
}
.nav h1 li a{
    text-decoration: none;
    color:black;
    font-family:\9ED1\4F53 ;
    font-size: 20px;
    width: 460px;
    position: relative;
    line-height: 30px;
    margin-left: 10px;
}

</style>

对的，谢谢你