#menu ul li { display: inline; }

#menu ul li a {
    padding: 2px 10px;
    display: inline-block;
    background-color:#EDEDED;
    color: #333;
    text-decoration: none;
    border-bottom:3px solid #EDEDED;
}
#menu ul li a:hover {
    background-color:#D6D6D6;
    color: #6D6D6D;
    border-bottom:3px solid #EA0000;
}

.div {
    width: 404px;
    border: 1px solid black;
    padding: 8px;
}

.header {
    margin-bottom: 10px;
	margin-left:300px; 
	margin-top:20px; 
	width:30px; 
}

#header input {
    width: 400px;
    height: 40px;
    border: 1px solid black;
    text-align: right;
}

.numberFields {
    margin-left: 300px;
    width: 100px;
    font-size:0;
    overflow: auto;
    float: left;
}

#numberFields input {
    background-color: green;
    border: 1px solid black;
    width: 120px;
    height: 40px;
}

#numberFields input[name="0"] {
    width: 360px;
}

#operations {
    margin-left: 4px;
    width: 40px;
    font-size: 0;
    display: inline-block;
}

#operations input {
    background-color: purple;
    border: 1px solid black;
    width: 40px;
    height: 40px;
}

#sum {
    margin-top: 5px;
}

#sum input {
    background-color: purple;
    border: 1px solid black;
    width: 404px;
    height: 40px;
}

<style>
* {box-sizing: border-box;}
ul {list-style-type: none;}
body {font-family: Verdana, sans-serif;}

.month {
    padding: 70px 25px;
    width: 100%;
    background: #1abc9c;
    text-align: center;
}

.month ul {
    margin: 0;
    padding: 0;
}

.month ul li {
    color: white;
    font-size: 20px;
    text-transform: uppercase;
    letter-spacing: 3px;
}

.month .prev {
    float: left;
    padding-top: 10px;
}

.month .next {
    float: right;
    padding-top: 10px;
}

.weekdays {
    margin: 0;
    padding: 10px 0;
    background-color: #ddd;
}

.weekdays li {
    display: inline-block;
    width: 13.6%;
    color: #666;
    text-align: center;
}

.days {
    padding: 10px 0;
    background: #eee;
    margin: 0;
}

.days li {
    list-style-type: none;
    display: inline-block;
    width: 13.6%;
    text-align: center;
    margin-bottom: 5px;
    font-size:12px;
    color: #777;
}

.days li .active {
    padding: 5px;
    background: #1abc9c;
    color: white !important
}

/* Add media queries for smaller screens */
@media screen and (max-width:720px) {
    .weekdays li, .days li {width: 13.1%;}
}

@media screen and (max-width: 420px) {
    .weekdays li, .days li {width: 12.5%;}
    .days li .active {padding: 2px;}
}

@media screen and (max-width: 290px) {
    .weekdays li, .days li {width: 12.2%;}
}
</style>

.imagem{
	width:100px;
	height:100px; 
	margin-left:100px;
	
}
.robo{ 
	margin-left:500px;
	margin-bottom:100px; 
}
.clock{	
	overflow:hidden;
	border:0;
	margin:0;
	padding:0;
	width:450px;
	height:450px;	
	margin-left:400px; 
	margin-top:70px; 
}
.about{ 
width:300px; 
text-align:justify;
background:#CF080E;
color:White;
padding:50px; 
	margin-left:250px; 
	
}