body {
    max-width: 750px;
}

h1 {
    font-size: 24px;
}

floor {
    max-width: 750px;
    left: 50%;
    margin-left: -375px;
}

.Feed_box {
    position: fixed;
    left: 50%;
    bottom: 0;
    max-width: 750px;
    margin-left: -375px;

    height: 80vh;
    z-index: 200;
    border-top: 1px solid #ebeced;
    background-color: #FFF;
}

.feed_input_box{
    width: 80%;
    display: flex;
}
.feed_input_box input {
    height: 35px;
}
.input_you{
    width: 20%;
    margin-right: 2%;
}
.input_zuo{ 
    width: 78%;
}

.header_taget {
    display: flex;
    right: 1%;
}

.header_logo {
    display: block;
    left: 1%;
}

.header_navigation {    
    overflow: hidden;
}

.header_nav_ul {
    width: 600px;
}

.phoneHide{
    display: block;
}