title: Can't find R class
body: <p>When i open eclipse, the <code>R class</code> in my project is disappeared. Why?<br>
  I've eclipse juno and the last version of android SDK.  </p>
  
  <p>The <code>R class</code> doesn't regenerate because there are errors in the code...<br>
  How can i solve this problem?</p>