我如何从我的网站代码删除白色边框?

Here's my JSFiddle

这是我的JSFiddle

html, body {
     height: 100%;
}
    #background {
        height: 100%;
        background: url(https://phosproject.com/wp-content/themes/phos_theme/images/7.jpg); no-repeat center center fixed; 
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}
.button {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 440px;
    height: 460px;
    margin-top: -230px; /* Half the height */
    margin-left: -220px; /* Half the width */

}
html, body