* {
	box-sizing: border-box;
	}

#float20, #float21, #float22, #float23 {
	float:left;
	text-align: center;
	border: 1px solid black;
	width: 50%;
	/*background-color: yellow;*/
	padding: 1px;
	/*margin: 2px;*/

	display: flex;
  	justify-content: center;
  	align-items: center;
	}

#float20:hover, #float21:hover, #float22:hover, #float23:hover {
	Background-color: yellow;
 }

@media only screen and (min-width: 600px){
#main {
 width: 600px;
 margin: auto;
 text-align: justify;
 }

#float20, #float21, #float22, #float23 {
	height: 150px;
 }
}

@media only screen and (max-width: 599px){
#main {
 width: 95%;
 text-align: justify;
 }
#float20, #float21, #float22, #float23 {
	width: 100%;
	padding: 20px;
}
}





.link, .link a {
 text-decoration : none;
}

.link:hover {
 background-color: yellow;
}

.clear {
 clear:both;
}