title: manipulate color of browser window when scrolling beyond the top or bottom
body: <p>When I scroll using trackpad there is a white gap between toolbar and the main window(above THIS IS TOP heading). You can see it in the images I attached. This gap ONLY appears when I scroll beyond the top or bottom at the bottom of the window with trackpad(not mouse). How can I set the color of that background beyond the "normal" window?</p>
  
  <p><a href="https://i.stack.imgur.com/DraM5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DraM5.png" alt="enter image description here"></a></p>
  
  <p>// When I don't scroll:</p>
  
  <p><a href="https://i.stack.imgur.com/TMakD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TMakD.png" alt="enter image description here"></a></p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>    @import url("960_12_col.css");
      
      #header{
      background-color: blue;
      height: 400px;
      margin-top: 80px;
      margin-bottom: 30px;
      color: white;
      padding-left: 50px;
      padding-top: 40px;
      box-sizing: border-box;
      }
      .grid_4{
      /* 
      text-align: center;
      background-color: red;
      margin-top: 30px;
      height: 250px;
      border: 20px solid black;
      box-sizing: border-box;
       */
      
      }
      .grid_3{
      padding:10px;
      border: 5px solid black;
      margin: 10px;
      height: 140px;
      box-sizing: border-box;
      }
      #comment1{
      text-align: left;
      }
      #comment2{
      text-align: center;
      }
      #comment3{
      text-align: center;
      }
      #comment4{
      text-align: right;
      }
      
      #leftImage{
      }
      
      #centerImage{
      }
      #rightImage{
      }
      .image{
      text-align: center;
      background-color: red;
      margin-top: 30px;
      height: 250px;
      border: 20px solid black;
      box-sizing: border-box;
      
      }
      .text{
      text-align: left;
      background-color: #C6E2FF;
      margin-top: 5px;
      height: 50px;
      border: 5px solid black;
      box-sizing: border-box;
      
      }
      body{
      /* 
      background-image: url("images/kaktus2.jpg");
      background-repeat:repeat;
       */
       
      background-image: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#66cccc), to(#336666));
      /* Safari 5.1+, Chrome 10+ */
      background-image: -webkit-linear-gradient(#336666, #66cccc); 
      background-attachment: fixed;
      /* background-color: red; */
      
      }
      
      #top{
      position:fixed;
      /* 
      margin:0px;
       */
      top:0px;
      left:80px;
      
      right:80px;
       */
      text-align: center;
      height: 80px;
      background-color: magenta;
      
      
      }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>    &lt;!DOCTYPE html&gt;
      &lt;html&gt;
        &lt;head&gt;
      &lt;!--   &lt;link rel="stylesheet" type="text/css"  href="css/960_12_col_rtl.css"&gt; --&gt;
        &lt;link href="css/custom.css" type="text/css" rel="stylesheet"&gt;
        &lt;/head&gt;
       &lt;body&gt;
       &lt;div id="top" class="grid_12"&gt; &lt;h1&gt;THIS IS TOP&lt;/h1&gt;&lt;/div&gt;
       &lt;div class="container_12 clearfix"&gt;
        &lt;div id="header" class="grid_12"&gt;
         &lt;h1&gt;HUHUHUHU&lt;/h1&gt;
          &lt;/div&gt;
          &lt;div id="comment1" class="grid_3"&gt;
           &lt;p&gt;This is comment 1!&lt;/p&gt;
        &lt;/div&gt;
        &lt;div id="comment2" class="grid_3"&gt;
           &lt;p&gt;This is comment 2!&lt;/p&gt;
        &lt;/div&gt;
        &lt;div id="comment3" class="grid_3"&gt;
           &lt;p&gt;This is comment 3!&lt;/p&gt;
        &lt;/div&gt;
        &lt;div id="comment4" class="grid_3"&gt;
           &lt;p&gt;This is comment 4!&lt;/p&gt;
        &lt;/div&gt;
       
          &lt;div class="grid_4 image" &gt;
           &lt;p id="image1"&gt;image1&lt;/p&gt;
          &lt;/div&gt;    
          &lt;div class="grid_4 image"&gt;
           &lt;p id="image2"&gt;image2&lt;/p&gt;
          &lt;/div&gt;
          &lt;div class="grid_4 image"&gt;
           &lt;p id="image3"&gt;image3&lt;/p&gt;
          &lt;/div&gt;
          
          
          &lt;div id="underLeftImage" class="grid_4 text"&gt;
           &lt;p id="underLeftImageText"&gt;image3&lt;/p&gt;
          &lt;/div&gt;
              
          &lt;div id="underCenterImage" class="grid_4 text"&gt;
           &lt;p id="underCenterImageText"&gt;image3&lt;/p&gt;
          &lt;/div&gt;    
          &lt;div id="underRightImage" class="grid_4 text"&gt;
           &lt;p id="underRightImageText"&gt;image3&lt;/p&gt;
          &lt;/div&gt;
       &lt;/div&gt;
       &lt;/body&gt;
      &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>