doc change only: add screens support doc

               <span class="zh-TW">最佳實務</span>

    </h2>

    <ul>

      <li><a href="<?cs var:toroot ?>guide/practices/screens_support.html">

            <span class="en">Supporting Multiple Screens</span>

          </a></li>

      <li class="toggle-list">

        <div><a href="<?cs var:toroot ?>guide/practices/ui_guidelines/index.html">

               <span class="en">UI Guidelines</span>

              </a></li>

        </ul>

      </li>

      </ul>

      <ul>

      <li><a href="<?cs var:toroot ?>guide/practices/design/performance.html">

            <span class="en">Designing for Performance</span>

          </a></li>

or scale them up by a factor of 1.5 (high dpi screens).

The screen density is expressed as dots-per-inch (dpi).</p>

<p>Currently supported densities:</p>

<ul>

  <li>Low density: 120 dpi</li>

  <li>Medium density: 160 dpi</li>

  <li>High density: 240 dpi</li>

</ul>

<p>Table of display types:</p>

<table>

<tr>

  <th></th><th>Low Density</th><th>Medium Density</th><th>High Density</th>

</tr>

<tr>

  <th>Small Screen</th>

  <td>QVGA</td>

  <td>n/a</td>

  <td>VGA</td>

</tr>

<tr>

  <th>Normal Screen</th>

  <td>WQVGA</td>

  <td>HVGA</td>

  <td>WVGA, FWVGA</td>

</tr>

<tr>

  <th>Large Screen</th>

  <td>n/a</td>

  <td>VGA, WVGA, FWVGA</td>

  <td>n/a</td>

</tr>

</table>

</dd> 

<p>For more information, see 

<a href="{@docRoot}guide/practices/screens_suppport.html">Multiple Screens Support</a>.</p>

<dt>attributes:</dt>

<dt>see also:</dt>

<dd>

  <ul>

    <li><a href="{@docRoot}guide/practices/screens_suppport.html">Multiple Screens Support</a></li>

    <li>{@link android.util.DisplayMetrics}</li>

  </ul>

</dd>