| <html><head> | 
 | <meta name="viewport" content="width=device-width"> | 
 | <style> | 
 | .d1 {position:fixed; top:5; right:5; z-index:2; overflow:hidden;} | 
 | .o {background:green; height:40px; width:200px;} | 
 | .t { width:2000px; height:198px; background-color: lightgray; border: 1px solid blue;} | 
 | body { margin: 0px; } | 
 | </style> | 
 | <script> | 
 |  | 
 | var fixed; | 
 |  | 
 | function remove_child() | 
 | { | 
 |   fixed = document.getElementById("d1"); | 
 |   fixed.parentElement.removeChild(fixed); | 
 | } | 
 |  | 
 | function add_child() | 
 | { | 
 |   document.body.appendChild(fixed); | 
 | } | 
 |  | 
 | </script> | 
 | </head> | 
 | <body> | 
 | <div class="d1" id="d1"><div class="o">This is a test</div></div> | 
 | <div class="t"> | 
 | 000 | 
 | </div> | 
 | <div class="t"> | 
 | 200<br> | 
 | <button onclick="remove_child();">remove fixed</button> | 
 | </div> | 
 | <div class="t"> | 
 | 400<br> | 
 | <button onclick="add_child();">add fixed</button> | 
 | </div> | 
 | <div class="t"> | 
 | 600<br> | 
 | </div> | 
 | <div class="t"> | 
 | 800 | 
 | </div> | 
 | <div class="t"> | 
 | 1000 | 
 | </div> | 
 | <div class="t"> | 
 | 1200 | 
 | </div> | 
 | <div class="t"> | 
 | 1400 | 
 | </div> | 
 | <div class="t"> | 
 | 1600 | 
 | </div> | 
 | <div class="t"> | 
 | 1800 | 
 | </div> | 
 | <div class="t"> | 
 | 2000 | 
 | </div> | 
 | <div class="t"> | 
 | 2200 | 
 | </div> | 
 | <div class="t"> | 
 | 2400 | 
 | </div> | 
 | <div class="t"> | 
 | 2600 | 
 | </div> | 
 | <div class="t"> | 
 | 2800 | 
 | </div> | 
 | <div class="t"> | 
 | 3000 | 
 | </div> | 
 | <div class="t"> | 
 | 3200 | 
 | </div> | 
 | <div class="t"> | 
 | 3400 | 
 | </div> | 
 | <div class="t"> | 
 | 3600 | 
 | </div> | 
 | <div class="t"> | 
 | 3800 | 
 | </div> | 
 | <div class="t"> | 
 | 4000 | 
 | </div> | 
 | </body></html> |