@media only screen and (max-width:300px){
header{
    height: 260px;
}
.logo_div{
    width: 100%;
}
#log_in_form span{
    display: block;
}
.sign_btn{
    font-size: 14px;
}
.log_div{
    width: 100%;
    height: 140px;
}
.nav_div{
    padding-top: 10px;
    display: inline-block;
}
.circle_img{
    width: 70px;
    max-height: 70px;
}
.item_div{
    width: 100%;
    height: 130px;
   
}
.img_area{
    height: 85%;
}

.txt_div{
    font-size: 12px;
}
.more_btn{
    margin: 0px;
}
/**/
@media only screen and (max-width:170px){
    .log_div{
        display: none;
    }
}
}