* {
    box-sizing:border-box;
}

img {
    max-width:100%;
}

body {
    background:#91d8d4;
}

header {
    background:lightcoral;
    padding:10px;
    margin:10px;
}

main {
    background:lightpink;
    padding:10px;
    margin:10px;
}

.class {
    background:#a7a7de;
}

/* id is the most specific identifier declaration */
#id {
    background:#f0e997;
}

footer {
    background:lightpink;
    padding:10px;
    margin:10px;
}

/* rules declared lower in the stylesheet are more specific */
footer {
    background:lightsteelblue;
}