Untitled

<head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <link rel="stylesheet" href="bootstrap/css/bootstrap.css" type="text/css" />
        <link rel="stylesheet" href="style.css" type="text/css" />
</head>

/* Main css */

@media only screen and (min-width: 1px) and (max-width: 320px){
    /* content */
}
@media only screen and (min-width: 321px) and (max-width: 600px){
    /* content */
}
@media only screen and (min-width: 601px) and (max-width: 768px){
    /* content */
}
@media only screen and (min-width: 769px) and (max-width: 1020px){
    /* content */
}

@media only screen and (max-width: 320px){
    /* content */
}

@media only screen and (max-width: 600px){
 /* content */
}

@media only screen and (max-width: 768px){
    /* content */
}

@media only screen and (max-width: 1020px){
    /* content */
}