<img id="aw_popup_close_btn" onclick="Popup.hideWindow();return false;"
         src="<?php echo $this->getSkinUrl('popup/images/close_label.gif');?>" >

<img id="aw_popup_close_btn" onclick="Popup.hideWindow();return false;"
         src="<?php echo $this->getSkinUrl('images/close.gif');?>" alt="hello" >