main.css

* {
    box-sizing: border-box;
}

.row{
	max-width: 1500px;
    margin: auto;
}

.row::after {
    content: "";
    clear: both;
    display: table;
}


.col-1 {width: 8.33%;}
.col-2 {width: 16.66%;}
.col-3 {width: 25%;}
.col-4 {width: 33.33%; max-width: 400px; margin: auto;}
.col-5 {width: 41.66%;}
.col-6 {width: 50%;}
.col-7 {width: 58.33%;}
.col-8 {width: 66.66%; max-width: 800px; margin: auto;}
.col-9 {width: 75%;}
.col-10 {width: 83.33%;}
.col-11 {width: 91.66%;}
.col-12 {width: 100%;}
	
[class*="col-"] {
    float: left;
    padding: 15px;
    border: none;
}

/* Extra small devices (phones, 600px and down) */
@media only screen and (max-width: 600px) {
	[class*="col-"] {
		width: 100%;
	}
}

/* Small devices (portrait tablets and large phones, 600px and up) */
@media only screen and (min-width: 600px) {

}

/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) {

} 

/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) {
} 

/* Extra large devices (large laptops and desktops, 1200px and up) */
@media only screen and (min-width: 1200px) {


}

.footer {
	background-color: gray;
}