function HeadSlider(){
$("#HeadSlider").show();
}
<div id="HeadSlider" class="fadeInDown">
<h1>请问大所多 <h1>请问大所多</h1>
<h1>请问大所多</h1>
<h1>请问大所多</h1>
</h1>
</div>
<button type="button" onclick="HeadSlider()">下拉</button>
#HeadSlider{
position:fixed;
top:0;
left:0;
right:0;
height:auto;
background-color:gray;
display:none;
-webkit-animation-duration: 0.3s;
animation-duration: 0.3s;
}