flexを使った例

application.css

/** * Eric Meyer's Reset CSS v2.0 (http://meyerweb.com/eric/tools/css/reset/) * http://cssreset.com */html, body, div, span, applet, object, iframe,h1, h2, h3, h4, h5, h6, p, blockquote, pre,a, abbr, acronym, address, big, cite, code,del, dfn, em, img, ins, kbd, q, s, samp,small, strike, strong, sub, sup, tt, var,b, u, i, center,dl, dt, dd, ol, ul, li,fieldset, form, label, legend,table, caption, tbody, tfoot, thead, tr, th, td,article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary,time, mark, audio, video {	margin: 0;	padding: 0;	border: 0;	font-size: 100%;	font: inherit;	vertical-align: baseline;}/* HTML5 display-role reset for older browsers */article, aside, details, figcaption, figure, footer, header, hgroup, menu, nav, section {	display: block;}body {	line-height: 1;}ol, ul {	list-style: none;}blockquote, q {	quotes: none;}blockquote:before, blockquote:after,q:before, q:after {	content: '';	content: none;}table {	border-collapse: collapse;	border-spacing: 0;}
/* formのときに青い線を出さなくする 外したり付けたりしてどうなるか見てみよう */
input,
textarea,
select {
  -webkit-tap-highlight-color: transparent;
  outline: none;
}
/* ここにCSSを書いてデザインを入れよう */
body {
  color: #444;
  background-color: #aaa;
}

.container {
  width: 980px;
  margin-left: auto;
  margin-right: auto;
  background-color: #666;
  box-shadow: rgba(0, 0, 0, .4) 0 0 8px;
  overflow: hidden;
}

.header {
  background-color: #999;
  color: #444;
}
.header__title {
  font-size: 42px;
  font-weight: bold;
  line-height: 1.4;
  text-align: center;
  padding-top: 40px;
  padding-bottom: 40px;
  text-shadow: rgba(255, 255, 255, .4) 0 1px 0;
}

.global-nav{
  background-color: #ccc;
  box-shadow: rgba(0, 0, 0, .4) 0 1px 1px;
  position: relative;
}
.global-nav__items {
  display: flex;
}
.global-nav__item {
  display: block;
  flex: 0 0 20%;
}
.global-nav__link {
  text-decoration: none;
  display: block;
  font-size: 16px;
  font-weight: bold;
  line-height: 64px;
  text-align: center;
  color: #444;
  text-shadow: rgba(255, 255, 255, .6) 0 1px 0;
  background: linear-gradient(to bottom, #ddd 0%, #ccc 100%);
}
.global-nav__link:hover,
.global-nav__item:nth-child(even) .global-nav__link:hover {
  background-color: #eee;
}
.global-nav__item:nth-child(even) .global-nav__link {
  background-color: #bbb;
  background: linear-gradient(to bottom, #bbb 0%, #aaa 100%);
}

.bread-crumbs {
  padding-left: 16px;
  padding-right: 16px;
  background-image: linear-gradient(to bottom, #666666 0%, #555555 100%);
}
.bread-crumbs__items {
  display: flex;
}
.bread-crumbs__item {
  display: block;
  position: relative;
  padding-right: 24px;
}
.bread-crumbs__item:before {
  content: ">";
  font-size: 13px;
  width: 24px;
  line-height: 32px;
  color: #aaa;
  text-align: center;
  position: absolute;
  right: 0;
  top: 0;
}
.bread-crumbs__item.is-current {
  padding-right: 0;
}
.bread-crumbs__item.is-current:before {
  content: none;
}
.bread-crumbs__link {
  color: #fff;
  font-size: 13px;
  text-decoration: none;
  line-height: 32px;
}
.top-ads {
  background-color: #ccc;
  padding: 16px 8px;
}
.top-ads__items {
  display: flex;
  justify-content: space-around;
}
.top-ads__item {
  display: block;
  flex: 0 0 305px;
}
.top-ads__image {
  width: 100%;
  height: auto;
}
.body {
  display: flex;
  flex-direction: row-reverse;
}
.main {
  flex: 0 0 66%;
  box-sizing: border-box;
  background-color: #ddd;
}
.main-header {
  background-color: #eee;
  padding: 16px;
  position: relative;
  box-shadow: rgba(0, 0, 0, .3) 0 1px 1px;
  overflow: hidden;
}
.main-header:before {
  content: "";
  display: block;
  background-color: #aaa;
  width: 44px;
  height: 44px;
  position: absolute;
  right: -12px;
  top: -12px;
  box-shadow: rgba(0, 0, 0, .6) 0 1px 1px;
}
.main-header:after {
  content: "";
  display: block;
  background-color: #ccc;
  width: 44px;
  height: 44px;
  position: absolute;
  right: -22px;
  top: -22px;
  transform: rotate(-45deg);
}

.main-header__title {
  font-size: 36px;
  line-height: 1.4;
  font-weight: bold;
  padding-left: 46px;
  position: relative;
}
.main-header__title:before,
.main-header__title:after {
  content: "";
  display: block;
  width: 12px;
  height: 12px;
  position: absolute;
  border-right: 12px #444 solid;
}
.main-header__title:before {
  left: 0;
  top: 14px;
  background-color: #999;
  border-right-color: #444;
}
.main-header__title:after {
  left: 0;
  top: 26px;
  background-color: #444;
  border-right-color: #999;
}

.article {
  padding: 16px;
}
.article__title {
  font-size: 28px;
  line-height: 1.4;
  font-weight: bold;
  margin-bottom: 16px;
  padding-left: 24px;
  position: relative;
}
.article__title:before {
  content: "";
  display: block;
  width: 12px;
  height: 20px;
  position: absolute;
  background-color: #999;
  border-bottom: 20px #444 solid;
  left: 0;
  top: 0;
}
.article__sub-title {
  font-size: 24px;
  line-height: 1.4;
  font-weight: bold;
  margin-bottom: 16px;
  position: relative;
  padding-left: 24px;
}
.article__paragraph + .article__sub-title {
  margin-top: 24px;
}
.article__sub-title:before,
.article__sub-title:after {
  content: "";
  display: block;
  position: absolute;
}
.article__sub-title:before {
  width: 4px;
  height: 16px;
  background-color: #444;
  left: 0;
  top: 9px;
}
.article__sub-title:after {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 8px 12px;
  border-color: transparent;
  border-left-color: #444;
  left: 6px;
  top: 9px;
}
.article__sub-sub-title {
  font-size: 18px;
  line-height: 1.4;
  font-weight: bold;
  margin-bottom: 16px;
  position: relative;
  padding-left: 24px;
}
.article__sub-sub-title:before,
.article__sub-sub-title:after {
  content: "";
  display: block;
  position: absolute;
  width: 12px;
  height: 12px;
  border-radius: 50%;
}
.article__sub-sub-title:before {
  left: 0;
  top: 6px;
  background-color: #444;
}
.article__sub-sub-title:after {
  left: 8px;
  top: 6px;
  background-color: #999;
}
.article__paragraph,
.article__blockquote-paragraph {
  font-size: 16px;
  line-height: 1.8;
  margin-bottom: 16px;
}
.article__link {
  color: royalblue;
}
.article__strong {
  font-weight: bold;
  color: #000;
}
.article__blockquote {
  border-left: solid 6px #999;
  padding-top: 24px;
  padding-left: 24px;
  position: relative;
  margin-top: 40px;
  margin-left: 8px;
  margin-bottom: 32px;
}
.article__blockquote:before {
  position: absolute;
  left: -27px;
  top: -22px;
  content: '"';
  font-size: 68px;
  font-family: serif;
  color: #eee;
  text-align: center;
  line-height: 84px;
  background-color: #999;
  width: 48px;
  height: 48px;
  border-radius: 50%;
}
.article__unorder-list,
.article__order-list {
  margin-bottom: 16px;
  margin-left: 24px;
  list-style-position: outside;
}
.article__unorder-list {
  list-style: disc;
}
.article__order-list {
  list-style: decimal;
}
.article__order-list-item,
.article__unorder-list-item {
  line-height: 1.6;
  margin-bottom: 8px;
}
.article__image {
  max-width: 100%;
  height: auto;
  margin-left: auto;
  margin-right: auto;
  margin-bottom: 24px;
}
.article__paragraph + .article__image {
  margin-top: 8px;
}
.aside {
  flex: 0 0 34%;
  background-color: #666;
  padding: 16px;
  box-sizing: border-box;
}

.aside-ads {
  margin-bottom: 24px;
}
.aside-ads__item {
  margin-bottom: 8px;
}
.aside-ads__item:last-child {
  margin-bottom: 0;
}
.aside-ads__image {
  width: 100%;
  height: auto;
}
.local-nav__item:first-child .local-nav__link {
  border-radius: 4px 4px 0 0;
}
.local-nav__item:last-child .local-nav__link {
  border-radius: 0 0 4px 4px;
}
.local-nav__link {
  display: block;
  padding: 0 16px;
  font-size: 16px;
  line-height: 42px;
  text-decoration: none;
  background-color: #999;
  margin-bottom: 2px;
  color: #fff;
}
.local-nav__link:hover {
  background-color: #ccc;
}
.local-nav__link.is-current {
  background-color: #777;
  cursor: default;
}
.footer {
  background-color: #444;
  padding: 24px 16px;
  display: flex;
  flex-wrap: wrap;
}

.footer-nav {
  flex: 0 0 50%;
  display: flex;
}
.footer-nav__items {
  flex: 0 0 33.33%;
}
.footer-nav__item {
  line-height: 1.6;
  margin-bottom: 6px;
  font-size: 13px;
  position: relative;
  padding-left: 12px;
}
.footer-nav__item:after {
  content: ">";
  position: absolute;
  left: 0;
  top: 0;
  color: #ccc;
}
.footer-nav__link {
  color: #fff;
  text-decoration: none;
}
.about-author {
  flex: 0 0 50%;
  background-color: #ccc;
  margin-bottom: 32px;
  box-sizing: border-box;
  padding: 16px;
  border-radius: 4px;
  box-shadow: rgba(0, 0, 0, .5) 0 1px 1px inset, rgba(255, 255, 255, .3) 0 1px 1px;
}
.about-author__title {
  font-size: 14px;
  font-weight: bold;
  line-height: 1.4;
  margin-bottom: 16px;
}
.about-author__image {
  width: 88px;
  height: 88px;
  border-radius: 50%;
  float: left;
}
.about-author__descriptions {
  padding-left: 104px;
}
.about-author__term {
  display: block;
  width: 60px;
  position: absolute;
  font-size: 14px;
  line-height: 1.6;
  text-align: right;
}
.about-author__description {
  display: block;
  padding-left: 72px;
  margin-bottom: 8px;
  font-size: 14px;
  line-height: 1.6;
}
.footer-copyright {
  flex: 0 0 100%;
  display: block;
  text-align: center;
  font-size: 14px;
  color: #fff;
}

.form {
  background-color: #fff;
  padding: 24px;
}
.form__title {
  font-size: 24px;
  line-height: 26px;
  font-weight: bold;
  margin-bottom: 24px;
  position: relative;
  padding-left: 52px;
  overflow: hidden;
}
.form__title:before {
  content: "";
  display: block;
  width: 36px;
  height: 22px;
  border: #444 solid 2px;
  position: absolute;
  left: 0;
  top: 0;
}
.form__title:after {
  content: "";
  display: block;
  width: 36px;
  height: 36px;
  border: #444 solid 2px;
  position: absolute;
  left: 0;
  top: -28px;
  transform: rotate(-45deg);
}
.form-item {
  margin-bottom: 24px;
  position: relative;
  padding-left: 200px;
}
.form-item__label {
  font-size: 14px;
  font-weight: bold;
  text-align: right;
  width: 176px;
  display: block;
  position: absolute;
  left: 0;
  top: 0;
  padding-top: 8px;
}
.form-item__text-input {
  display: block;
  width: 100%;
  padding: 8px;
  box-sizing: border-box;
  border: solid 1px #ccc;
  border-radius: 4px;
}
.form-item__textarea {
  display: block;
  width: 100%;
  height: 320px;
  padding: 8px;
  box-sizing: border-box;
  border: solid 1px #ccc;
  border-radius: 4px;
}

.form-item__inline-items {
  font-size: 0;
}
.form-item__inline-item {
  display: inline-block;
  margin-right: 16px;
}

.form-item__radio {
  border: #ccc solid 1px;
  padding: 12px;
  font-size: 14px;
  border-radius: 4px;
  cursor: pointer;
  display: block;
  background-color: #eee;
}
.form-item__radio:hover {
  background-color: #ddd;
  box-shadow: rgba(0, 0, 0, .6) 0 1px 1px;
}

.form-item__radio-input {
  margin: 0 8px 0 0;
}

.form-item__checkbox {
  border: #ccc solid 1px;
  padding: 12px;
  font-size: 14px;
  border-radius: 4px;
  cursor: pointer;
  display: block;
  background-color: #ddd;
}
.form-item__checkbox:hover {
  background-color: #ccc;
  box-shadow: rgba(0, 0, 0, .6) 0 1px 1px;
}
.form-item__checkbox-input {
  margin: 0 8px 0 0;
}
.form-item__select-pull-down {
  width: 100%;
  border: #ccc solid 1px;
  background-color: #eee;
  padding: 4px;
  font-size: 14px;
  box-shadow: rgba(0, 0, 0, .2) 0 1px 0 inset;
}
.form-item__select-list {
  width: 100%;
  border: #ccc solid 1px;
  background-color: #eee;
  font-size: 14px;
  box-shadow: rgba(0, 0, 0, .2) 0 1px 0 inset;
  overflow: hidden;
}
.form-item__select-list-option {
  display: block;
  cursor: pointer;
  border-bottom: #ccc solid 1px;
  padding: 8px;
}
.form-item__select-list-option:last-child {
  border-bottom: none;
}
.form-item__file-contaner {
  position: relative;
  height: 32px;
}
.form-item__file {
  height: 32px;
  width: 100%;
  cursor: pointer;
  background-color: #eee;
  border: #ccc solid 1px;
  border-radius: 4px;
  padding: 6px;
  box-sizing: border-box;
  box-shadow: rgba(0, 0, 0, .2) 0 1px 0 inset;
}
.form-item__actions-items {
  text-align: center;
  font-size: 0;
}
.form-item__actions-item {
  display: inline-block;
  padding-left: 8px;
  padding-right: 8px;
  width: 50%;
  box-sizing: border-box;
}
.form-item__action {
  display: block;
  width: 100%;
  border: #aaa solid 1px;
  border-radius: 4px;
  cursor: pointer;
  height: 38px;
  font-size: 14px;
}
.form-item__action.is-submit {
  background-color: #444;
  color: #fff;
  border-color: #222;
  box-shadow: rgba(0, 0, 0, .1) 0 1px 1px, rgba(255, 255, 255, .2) 0 1px 0 inset;
  text-shadow: rgba(0, 0, 0, .4) 0 -1px 0;
}
.form-item__action.is-reset {
  background-color: #ccc;
  color: #444;
  border-color: #aaa;
  box-shadow: rgba(0, 0, 0, .1) 0 1px 1px, rgba(255, 255, 255, .6) 0 1px 0 inset;
  text-shadow: rgba(255, 255, 255, .8) 0 1px 0;
}