trinidad ppr status: how to show in the window center for both IE and Firefox

[Dave]

<tr:statusIndicator>
  <f:facet name="busy">
    <tr:outputText value="Processing..." styleClass="ajaxStatus"/>
  </f:facet>
</tr:statusIndicator>
 
we like to show the "Processing..." in the window center for Firefox and IE. 
What the style ajaxStatus should be?
 
It is best to disable user input during processing if possible.
 
Thanks,
Dave