title: change style list image onclick + to -
body: <p>Hello everybody I hope you are all fine
   please help me to resolve this problem,I am confused with this, 
  when  "onclick" I want that the + become - like this attached image.
  remember that that + and - are images named image 'puceplus.png' and 'pucemoins.png'</p>
  
  <pre class="lang-css prettyprint-override"><code>#ulist li:before {
      content: url('puceplus.png');
      margin-right: 4px;
  }
  </code></pre>
  
   <pre class="lang-html prettyprint-override"><code>&lt;ul id="ulist"&gt;
              &lt;li  onclick="hideshow('usublist1')"&gt;
                  Gestion des données clients
                  &lt;ul id="usublist1" style="display:none;" class="sublist"&gt;
                      &lt;li &gt;
                         Centraliser vos données clients et éviter les redondances
                        &lt;/li&gt;
  
                  &lt;/ul&gt;
              &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>