動畫功能不工作DIV

Question

我想讓一個div從關閉屏幕到關於屏幕......該div應該從上到下。我已經嘗試了一些東西，但遺憾的是沒有任何反應:(。我是對的，在div必須position: absolute;？

請幫助。

HTML + JQUERY

<div id="nav"> 
    <a href="#"><span>1</a> 
    <a href="#"><span>2</a> 
    <a href="#"><span>3</a> 
    <a href="#"><span>4</a>  
    <a href="#"><span>5</a> 
</div> 

<div id="hidden"> 
    <h1>Text</h1> 
    <p>Text</p> 
</div> 

<script> 
    var main = function() { 

     $('#nav a:nth-child(1)').click(function() { 
      $('#hidden').animate({ 
       top: +=500px 
      }, 1000); 
     }); 
    }; 
    $(document).ready(main); 
</script> 

CSS

body { 
    background-image: url("http://static.tumblr.com/97f4b171db68d6ef1836c8fcb9a1c1a3/oi8jcug/xIcn5vql3/tumblr_static_aajc47nn2ds8c0k004gskoo0c.jpg"); 
    background-repeat: no-repeat; 
    background-size: cover; 
    padding: 0px; 
    margin: 0px; 
} 

a { 
    outline: none; 
} 

#nav { 
    height: 50px; 
    line-height: 50px; 
    background-color: #1C1C1C; 
    font-size: 0px; 
    text-decoration: none; 
    width: 100%; 
    text-align: center; 
    font-family: sans-serif; 
    margin-bottom: none; 
} 

#nav span { 
    display: inline-block; 
    font-size: 25px; 
    padding-left: 10px; 
    padding-right: 10px; 
    text-align: center; 
    border-right: 1px solid white; 
    height: 50px; 
} 

#nav span:first-child { 
    border-left: 1px solid white; 
} 

#nav span:hover { 
    border-bottom: 2px solid white; 
} 

#nav a { 
    color: white; 
    text-decoration: none; 
    margin: 0px; 
    padding: 0px; 
} 

#hidden { 
    width: 100%; 
    height: 200px; 
    padding-left: 30px; 
    background-color: #1C1C1C; 
    color: red; 
    font-size: 10px; 
    top: -250px; 
    position: absolute; 
} 

謝謝， HydraCles

Answer 1

改變

$('#nav a:nth-child(1)').click(function() { 
     $('#hidden').animate({ 
      top: +=500px 
     }, 1000); 
    }); 

與

$('#nav a:nth-child(1)').click(function() { 
    $('#hidden').animate({ 
     top: '+=500px' 
    }, 1000); 
});