title: What is meaning for -- (at 'cardBackgroundColor' with value '?android:attr/colorBackgroundFloating')
body: <p>I have got a problem while download a project from github.
  Error is as:</p>
  
  <p>F:\Tikam\Sample Project\Advance Design Project\ActivitySceneTransitionBasic\Application\build\intermediates\exploded-aar\com.android.support\cardview-v7\23.3.0\res\values-v23\values-v23.xml
  Error:(3, 5) No resource found that matches the given name (at 'cardBackgroundColor' with value '?android:attr/colorBackgroundFloating').
  Error:Execution failed for task ':Application:processDebugResources'.</p>
  
  <pre><code>Error:(3, 5) No resource found that matches the given name (at 'cardBackgroundColor' with value '?android:attr/colorBackgroundFloating').
  </code></pre>
  
  <blockquote>
    <p>com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command 'F:\Android Development\sdk\build-tools\23.0.3\aapt.exe'' finished with non-zero exit value 1</p>
  </blockquote>
  
  <p>my v23\values-v23.xml file is as:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;resources&gt;
      &lt;style name="CardView" parent="Base.CardView"&gt;
          &lt;item name="cardBackgroundColor"&gt;?android:attr/colorBackgroundFloating&lt;/item&gt;
      &lt;/style&gt;
  &lt;/resources&gt;
  </code></pre>