The ZoomPanel control is a compact collecton of 3 zoom controls: a OpenLayers.Control.ZoomIn, a OpenLayers.Control.ZoomToMaxExtent, and a OpenLayers.Control.ZoomOut. By default it is drawn in the upper left corner of the map.
If you wish to use this class with the default images and you want it to look nice in ie6, you should add the following, conditionally added css stylesheet to your HTML file:
<!--[if lte IE 6]> <link rel="stylesheet" href="../theme/default/ie6-style.css" type="text/css" /> <![endif]-->