html插入代码：

<div class="cbgg">
<p>本站已稳定运行了 <script language= "JavaScript" type= "text/javascript" >
var urodz= new Date ( "01/15/2021" );
var now = new Date ();
var ile = now.getTime() - urodz.getTime();
var dni = Math. floor (ile / (1000 * 60 * 60 * 24));
document.write(+dni)
</script> 天</p>
</div>

css样式代码：

.cbgg {
    padding: 10px;
    background-color: #fff;
}

.cbgg p {
    text-align: center;
}