body {
	background-color: yellow;

}



@media (max-width: 600px) {
    body {
        background: purple  ;
    }

div.uno {
margin-left:auto;
	margin-right:auto;
    max-width: 500px;
    background: red;
    padding: 25px 15px 25px 10px;
    font: 12px Georgia, "Times New Roman", Times, serif;
    color: #888;
    text-shadow: 1px 1px 1px #FFF;
    border:1px solid #E4E4E4;

}


div.dos {

margin-left:auto;
	margin-right:auto;
    max-width: 500px;
    background: orange;
    padding: 25px 15px 25px 10px;
    font: 12px Georgia, "Times New Roman", Times, serif;
    color: #888;
    text-shadow: 1px 1px 1px #FFF;
    border:1px solid #E4E4E4;


}



div.tres {
margin-left:auto;
	margin-right:auto;
    max-width: 500px;
    background: blue;
    padding: 25px 15px 25px 10px;
    font: 12px Georgia, "Times New Roman", Times, serif;
    color: #888;
    text-shadow: 1px 1px 1px #FFF;
    border:1px solid #E4E4E4;


}



div#cuatro {

margin-left:auto;
	margin-right:auto;
    max-width: 500px;
    background: green;
    padding: 25px 15px 25px 10px;
    font: 12px Georgia, "Times New Roman", Times, serif;
    color: #888;
    text-shadow: 1px 1px 1px #FFF;
    border:1px solid #E4E4E4;

}