Naming Lines in CSS Grid

Naming Lines in CSS Grid by Wes Bos

HTML

<link rel="stylesheet" href="https://cdn.rawgit.com/wesbos/css-grid/master/assets/style.css">
<div class="container">
  <div class="item item1">1</div>
  <div class="item item2">2</div>
  <div class="item item3">3</div>
  <div class="item item4">4</div>
  <div class="item item5">5</div>
  <div class="item item6">6</div>
  <div class="item item7">7</div>
  <div class="item item8">8</div>
  <div class="item item9">9</div>
  <div class="item item10">10</div>
  <div class="item item11">11</div>
  <div class="item item12">12</div>
  <div class="item item13">13</div>
  <div class="item item14">14</div>
  <div class="item item15">15</div>
  <div class="item item16">16</div>
  <div class="item item17">17</div>
  <div class="item item18">18</div>
  <div class="item item19">19</div>
  <div class="item item20">20</div>
  <div class="item item21">21</div>
  <div class="item item22">22</div>
  <div class="item item23">23</div>
  <div class="item item24">24</div>
  <div class="item item25">25</div>
  <div class="item item26">26</div>
  <div class="item item27">27</div>
  <div class="item item28">28</div>
  <div class="item item29">29</div>
  <div class="item item30">30</div>
</div>

CSS

.container {
  display: grid;
  grid-gap: 20px;
  grid-template-columns: [sidebar-start site-left] 1fr [sidebar-end content-start] 500px [content-end] 1fr [site-right];
  grid-template-rows: [content-top] repeat(10, auto) [content-bottom];
}

.item3 {
  background: slateblue;
  grid-column: content-start;
  grid-row: content-top / content-bottom;
  /* grid-row: 1 / span 10; */
}