Merge pull request twbs#20409 from nfatah/patch-1

update index.html

Author: patrickhlauke

docs/examples/grid/index.html

@@ -106,7 +106,7 @@ <h3>Mixed: mobile, tablet, and desktop</h3>
       <p></p>
       <div class="row">
         <div class="col-xs-12 col-sm-6 col-lg-8">.col-xs-12 .col-sm-6 .col-lg-8</div>
-        <div class="col-xs-6 col-lg-4">.col-xs-6 .col-lg-4</div>
+        <div class="col-sm-6 col-lg-4">.col-sm-6 .col-lg-4</div>
       </div>
       <div class="row">
         <div class="col-xs-6 col-sm-4">.col-xs-6 .col-sm-4</div>