body {
     background-color: lightcoral;
     font-family: "Lucida Sans Unicode", "Lucida Grande", sans-serif;

     display: flex;       /* all your children use flexbox */
     flex-direction: column;
     min-height: 100vh;   /* body takes up 100% of viewport */
}

img {
/*    width: 300px; */    

    max-width: 400px;
    min-width: 200px;
    width: 50%;

    float: left;  /* float around image, image on left */

    margin-right: 20px;  /* only set right margin */
    }

p {
    background-color: lightblue;
    margin: 30px;
    padding: 10px;
}

main {
     background-color: white;
     flex-grow: 1;  /* use up as much vertical space as possible */
}

footer {
       text-align: center;
       background-color: lightblue;
}