Mobile first pure CSS container taken from Bootstrap (breakpoints included)

container.css

/* 
usage: @import url("container.css"); at the top of your base stylesheet
*/

/* ------------ */
/* Mobile first */
/* ------------ */

.container {
  padding: 0 50px;
  margin-left: auto;
  margin-right: auto;
  max-width: 420px;
}

/* ------------ */
/* Break points */
/* ------------ */

/* Small devices (landscape phones, 576px and up) */
@media (min-width: 576px) {
  .container {
    max-width: 540px;
  }
}

/* Medium devices (tablets, 768px and up) */
@media (min-width: 768px) {
  .container {
    max-width: 720px;
  }
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) {
  .container {
    max-width: 960px;
  }
}

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
  .container {
    max-width: 1140px;
  }
}