#main_icon{
    background-image: url(../img/topic22.png);
    background-position: center center;
    background-repeat: no-repeat;
}

#main_submenu{ display: none; }

.nav_button{ width: 220px; }

table{
    position: relative;
    margin: auto;
    padding: 0;
    border-collapse: collapse;
	width: 75%;
}

td{
    border: 1px solid #000;
    padding: 2px;
    text-align: center;
	vertical-align: middle;
	width: 50%;
}

@media screen and (max-width: 600px){
    
    #main_nav .nav_button{
        display: none;
    }
    #main_submenu{
        display: block;
    }
    
}