How to make a confirm dialog <p:confirmDialog> down the page

Following is the p:confirmDialog code :

<p:confirmDialog id="popUpData" global="true" widgetVar="popUpData"
        header="#{app['data.fail']}" styleClass="Sdialog" 
        closable="false" draggable="true">

Below is the CSS code :

.Sdialog{
    width:50% !important;
    height:20% !important;
    top : 80% !important;
}

Want to just move the confirmDialog a bit down. But the pop up is not coming down and the changes are not getting reflected. Can you please help me here.Thanks in advance.