title: Duplicate Id. JSF
body: <p>I have a problem with JSF. Can anyone say why this doesn't work?</p>
  
  <pre><code>&lt;h:selectOneListbox
    id="lang" size="5"
    value="#{MbInstitution.node.lang}"
    valueChangeListener="#{MbInstitution.changeLanguage}"
    rendered="#{MbInstitution.view}"
    &gt;
   &lt;a4j:support event="onchange" reRender="shortDesc, fullDesc"/&gt;
   &lt;f:selectItems value="#{MbInstitution.languagesByInstitute}"/&gt;
  &lt;/h:selectOneListbox&gt;
  &lt;h:selectOneListbox
    id="lang" size="5"
    disabled="#{!MbInstitution.managingNew}"
    value="#{MbInstitution.node.lang}"
    rendered="#{!MbInstitution.view}"
    &gt;
   &lt;f:selectItems value="#{MbInstitution.availableLanguages}"/&gt;
  &lt;/h:selectOneListbox&gt;
  </code></pre>
  
  <p>It says: "duplicate Id for a component instForm:lang"
  I know that i have 2 elements with same Id, but one is rendered only when another isn't. So, i didn't think it would be a problem. Actually it's not a big problem at all as i don't need this id, but what if i needed then what would i do?</p>