div居中
.bgform {
top:50%;
left:50%;
position: absolute;
/*right: 10px;*/
/*bottom: 150px;*/
background: rgba(255, 255, 255, 0.20);
border: 1px solid rgba(183, 255, 255, 0.27);
border-radius: 2px;
width: 350px;
height: 350px;
padding: 5px auto;
margin:-175px 0 0 -175px;
}