*{
    box-sizing: border-box;
}

/*for mobile phones*/
[class*="col-"]{
    width: 100%;
}

body{
    margin: 0px;
}

/*for desktops*/
@media only screen and (min-width: 1024px){
    .col-1 {width: 8.33%;}
    .col-2 {width: 16.66%;}
    .col-3 {width: 25%;}
    .col-4 {width: 33.33%;}
    .col-5 {width: 41.66%;}
    .col-6 {width: 50%;}
    .col-7 {width: 58.33%;}
    .col-8 {width: 66.66%;}
    .col-9 {width: 75%;}
    .col-10 {width: 83.33%;}
    .col-11 {width: 91.66%;}
    .col-12 {width: 100%;}

    body {margin: 0px 100px 0px 100px;}
    div.row {
        max-width:900px;
        margin: 0px auto;
    }

}

[class*= "col-"]{
    float: left;
    border: none;
}

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

div.main {
  display: flex;
  flex-flow: column nowrap;
  max-width: 900px;
  margin: 0 auto;
}