grid class inconsistency 2

https://github.com/twbs/bootstrap/commit/32bde78e1996a92e6b801e1f4a475d5ab48685f8

docs/_includes/css/grid.html

@@ -347,10 +347,10 @@
 
 
   <h3 id="grid-nesting">Nesting columns</h3>
-  <p>To nest your content with the default grid, add a new <code>.row</code> and set of <code>.col-md-*</code> columns within an existing <code>.col-md-*</code> column. Nested rows should include a set of columns that add up to 12 or less (it is not required that you use all 12 available columns).</p>
+  <p>To nest your content with the default grid, add a new <code>.row</code> and set of <code>.col-sm-*</code> columns within an existing <code>.col-sm-*</code> column. Nested rows should include a set of columns that add up to 12 or less (it is not required that you use all 12 available columns).</p>
   <div class="row show-grid">
     <div class="col-sm-9">
-      Level 1: .col-md-9
+      Level 1: .col-sm-9
       <div class="row show-grid">
         <div class="col-xs-8 col-sm-6">
           Level 2: .col-xs-8 .col-sm-6