<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
            }
            .advert {
                width: 300px;
                height: 200px;
                background-color: black;
                position:fixed;
                right:0;
                bottom:0;
            }
            .advert:first-line {
                color: white;
            }
            .x{
                position:absolute;
                right:0;
                
            }
        </style>
    </head>
    <body>
    	<section class="advert">
            广告文案
            <button class="x">x</button>
        </section>

        <script>
            document.querySelector('button').onclick = function() {
                this.parentNode.style.display = 'none'
            }
        </script>
    </body>
</html>