massive CL is massive

src/site/_includes/docs/getting-started/_interface.html

 <section>
 <p>
 <em>Interfaces</em>&mdash;types that define
 which methods a class provides&mdash;are
 important in Dart.
 In fact, much of the Dart
 <a href="http://api.dartlang.org/dart_core/" target="_blank">Core Library</a>
 is defined in terms of interfaces.
 If you've never used a language
 that features interfaces or protocols,
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   <dt> <code>int</code> and <code>num</code> interfaces </dt>
   <dd>
     Although you might expect <code>int</code> and <code>double</code>
     to be primitive types,
     they're actually interfaces that
     extend the <code>num</code> interface.
     This means that <code>int</code> and <code>double</code> variables
     are also <code>num</code>s.
 
-<aside class="note">
-<b>Important:</b>
+<aside>
+  <div class="alert alert-info">
+    <strong>Tip:</strong>
 Be sure to initialize numbers.
 Because they're objects,
 their initial value is <code>null</code>,
 not 0.
+  </div>
 </aside>
 
     <p>
     In use, <code>int</code> and <code>double</code>
     feel like the primitive types you're probably used to.
     For example, you can use literals to set their values:
     </p>
 
 <pre>int height = 160;
 double rad = 0.0;</pre>
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 <h3> Try this </h3>
 
 {PENDING: add stuff if we think of anything}
 
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 </div>
 </section>