style1.css

* {
    box-sizing: border-box;
}

/* styling the header */
.header {
    background-color: pink;
    padding: 15px;
    text-align: center;
}

/* styling navigation */
.nav-menu {
    overflow: hidden;
    background-color: black;
}

.nav-menu a {
    float: left;
    text-align: center;
    display: block;
    color: cornsilk;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}

.nav-menu a:hover {
    background-color: rgb(240, 24, 240);
    color: white;
}

/* styling content layout */
.colA, .colB, .colC {
    float: left;
    width: 31%;
    padding: 15px;
    text-align: justify;
}

h2 {
    color: darkolivegreen;
    text-align: center;
}

.colB {
    text-align: center;
}

/* media query settings for responsive website */

/* size for tablets, setting it to 50% will create 2 columns */
@media screen and (max-width:600px) {
    .colA, .colB, .colC {
        width: 50%
    }
}
/* size for cellphones, setting it to 100% will create 1 column */
@media screen and (max-width:400px) {
    .colA, .colB, .colC {
        width: 100%
    }
}