📅  最后修改于: 2022-03-11 14:47:51.654000             🧑  作者: Mango
footer#site-footer{
position:relative;
}
footer#site-footer:before { /* use before property (pseudo-element) */
position: absolute;
content: '';
top: 0;
left: 0;
width: 100%;
height: 100%;
background: rgba(0,0,0,0.3);
}