<a href="#">弹幕技术</a>
  <div class="mask">
    <a href="#" class="button">X</a>
  </div>
  <!-- 底部发言框前端 -->
  <div class="bottom">
    <input class="content"></input>
    <a href="#" class="send">发表言论</a>
  </div>

html,body{
    background-image:url("images/208.jpg");
    height:100%;//文字的显示区域要设置好
  }
  div.mask{
    position:fixed;
    width:100%;
    height:100%;
    background-color:black;
    opacity:0.5;
    top:0px;
    left:0px;
  }
  div.bottom{
    width:100%;
    height:77px;
    background-color:#090909;
    position:fixed;
    bottom:0px;
    left:0px;
    text-align:center;
    line-height:77px;
  }
  div.bottom input.content{
    width:605px;
    height:37px;
    border:none;
    border-radius:10px 0px 0px 10px;
    font-size:16px;
    font-family:'Microsoft Yahei';
  }
  div.bottom a.send{
    background-color:green;
    color:#fff;
    display:inline-block;
    width:150px;
    height:40px;
    line-height:37px;
    text-align:center;
    position:relative;
    left:-10px;
    top:-2px;
    border-radius:0px 10px 10px 0px;
    text-decoration:none;
    font-family:'Microsoft Yahei';
  }
  div.mask a.button{
    width:50px;
    height:50px;
    border-radius:30px;
    background-color:#660000;
    color:#fff;
    position:fixed;
    top:20px;
    right:20px;
    text-align:center;
    line-height:50px;
    font-size:30px;
    font-family:'Microsoft Yahei';
    border:1px solid #fff;
    text-decoration:none;
    cursor:pointer;
  }
  div.text{
    color:#fff;
    position:fixed;
    right:0px;
    font-size:20px;
    white-space: nowrap;
  }

$('a.send').click(function(){
      //获取内容，创建新元素，并设置位置追加到目标元素中
      var val=$('input.content').val();
      var $content=$('<div class="text">'+val+'</div>');
      var top=Math.random()*$(document.body).height()-77;
      $content.css('top',top);
      $('div.mask').append($content);
      //移动到最右侧，直接删除该元素
      $content.animate({right:$(document.body).width()+100},8000,function(){
        $(this).remove();
      });
    });
    $('div.button').click(function(){
      $('div.mask').hide(2000);
    });