Answers for "div element in center of page"

center div in middle of page

.centered {
  position: fixed;
  top: 50%;
  left: 50%;
  /* bring your own prefixes */
  transform: translate(-50%, -50%);
}

align a div in center of another div

#container {
    width: 640px; /*can be in percentage also.*/
    height: auto;
    margin: 0 auto;
    padding: 10px;
    position: relative;
}