title: CSS disappearing in updatepanel
body: <p>i have this problem, i putted my whole page in the update panel , i have several <code>ASP:Pannel</code>
  with <code>Visible="false"</code> attribute.</p>
  
  <p>one of them containing <code>asp:RadioButtonList</code> With <code>Yes,No</code></p>
  
  <p>at the <code>Page_Load()</code> one of them get visible to the user with the radio button list.
  so when he press <code>Yess</code>, another panel get visible to him .</p>
  
  <p>the problem is i have a panel containing  <code>asp:DropDownList</code> with</p>
  
  <p><code>CssClass="span6 chzn-select"&gt;</code></p>
  
  <p>so when this panel get visible the <code>DropDownList</code> <code>css</code> disappear !.
  i know that there is a problem with the update panel post back , but i don't know how to solve this .
  also the <code>DropDownList</code> get the style from JQuery file called chosen but i don't have any script at any page , i just put the css class and it have it's style.
  thanks in advance.</p>