兼容性滚动顶部出现

<style>
#top_fixed {
    width: 100%;
    height: 50px;
    z-index: 999;
    max-width: 640px;
    min-width: 320px;
}
.top_fixed {
    width: 100%;
    height: 50px;
    background-color: #13a4db;
    overflow: hidden;
    position: fixed;
    top: 0;
    z-index: 99999;
}
.top_fixed p {
    width: 35%;
    height: 50px;
    line-height: 25px;
    text-align: center;
    color: #fff;
    font-size: 12px;
    font-weight: bold;
    float: left;
    margin-left: 2%;
}
.top_fixed a {
    display: inline-block;
    width: 60%;
    height: 36px;
    border-radius: 5px;
    line-height: 36px;
    text-align: center;
    background-color: #fff;
    color: #13a4db;
    float: right;
    margin-top: 7px;
    margin-right: 2%;
    font-size: 16px;
}
.top_fixed a span {
    font-size: 15px;
    font-weight: bold;
}
</style>
<div id="top_fixed" class="top_fixed" style="display:none">
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    </div>
    <script type="text/javascript">
    window.onresize=window.onscroll=window.onload=function(){
        var oSearch=document.getElementById("top_fixed");
        var bodyScrollTop=document.body.scrollTop||document.documentElement.scrollTop;
        if(bodyScrollTop>2){
            oSearch.style.display="block";

        }
        else{
            oSearch.style.display="none";
        }    
    }
    </script>