style.css

html,body,div,ul,form,dl,dt,dd {
    margin: 0;
    padding: 0;
}
a {
    text-decoration: none;
}
.container {
    width: 800px;
    margin: 0 auto;
    margin-bottom: 10px;
    overflow: hidden;
}
.hide {
    display: none;
}
.box {
    border: 1px solid #CCC;
    height: 500px;
    padding: 10px;
    overflow-y: scroll;
}
.box h3 {
    border-bottom: 1px solid #ccc;
    padding-bottom: 5px;
}
.message-list {
    width: 70%;
    float: left;

}
.message-list dl {
    margin-bottom: 20px;
}
.message-list dt {
    padding: 5px;
    background-color: #eee;
}
.message-list dd {
    padding: 10px;
}
.message-list time {
    color: #999;
}
.user-list {
    width: 20%;
    float: right;
}
.user-list li {
    cursor: pointer;
    padding: 5px;
}
.user-list li:hover {
    background-color: #eee;
}
.send-box {
    height: 80px;
}
.send-box textarea {
    height: 92%;
    width: 85%;
}
#btn-send {
    height: 100%;
    width: 13%;
    border: 1px solid #ccc;
    float: right;
    cursor: pointer;
    font-size: 20px;
}
.layer {
    position: absolute;
    width: 100%;
    height: 100%;
    left: 0;
    top: 0;
    background-color: #000;
    z-index: 8888;
    opacity: .5;
}
.login {
    position: absolute;
    width: 200px;
    height: 100px;
    background-color: #fff;
    padding: 20px;
    border: 1px solid #999;
    left: 150px;
    top: 100px;
    z-index: 9999;
}