Le bouton top de commentcamarche.net

   <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script> 
<script type="text/javascript"> 
$(function () { 
 var scroll_timer; 
 var displayed = false; 
 var $message = $('#message a'); 
 var $window = $(window); 
 var top = $(document.body).children(0).position().top; 
 $window.scroll(function () { 
  window.clearTimeout(scroll_timer); 
  scroll_timer = window.setTimeout(function () { 
   if($window.scrollTop() <= top) 
   { 
    displayed = false; 
    $message.fadeOut(500); 
   } 
   else if(displayed == false) 
   { 
    displayed = true; 
    $message.stop(true, true).show().click(function () { $message.fadeOut(500); }); 
   } 
  }, 100); 
 }); 
}); 
</script>

/* css pour la fonction " top " */   
{ 
 margin: 0; 
 padding: 0; 
} 
h1, p 
{ 
 margin: 48px; 
 line-height: 24px; 
} 
#message a 
{ 
 /* display: block before hiding */ 
 display: block; 
 display: none; 

 /* link is above all other elements */ 
 z-index: 999;  

 /* link doesn't hide text behind it */ 
 opacity: .8; 

 /* link stays at same place on page */ 
 position: fixed; 

 /* link goes at the bottom of the page */ 
 top: 100%; 
 margin-top: -80px; /* = height + preferred bottom margin */ 

 /* link is centered */ 
 left: 50%; 
 margin-left: -160px; /* = half of width */ 

 /* round the corners (to your preference) */ 
 -moz-border-radius: 24px; 
 -webkit-border-radius: 24px; 

 /* make it big and easy to see (size, style to preferences) */ 
 width: 300px; 
 line-height: 48px; 
 height: 48px; 
 padding: 10px; 
 background-color: /* BG #000*/ #DEEDF9; 
 font-size: 24px; 
 text-align: center; 
 color: /* BG #fff*/ #6699ff; 
}

<div id="top"></div>

 <div id="message"><a href="#top">Return to top</a></div>    
</body> 
</html>

,on_scroll:function(event){setTimeout(function(){var t=$j(window).scrollTop();if(!$ec._gtv&&t>=100){$ec._gtv=true;$j('#gotop').fadeIn();} 
else if($ec._gtv&&t<100){$ec._gtv=false;$j('#gotop').hide();}},200); 

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