According to the Open GIS Consortium Web Map Service (WMS) version 1.1.1 specifications, "layers may include a <ScaleHint> element that suggests minimum and maximum scale for which it is appropriate to display this layer." Minimum and maximum scales will be reported in the WMS service capabilities -
<a href='http://support.esri.com/en/knowledgebase/techarticles/detail/27948' target='_blank'>How To: View the WMS service capabilities</a> - and in the Layer Properties General Tab for the WMS service layer and all service sublayers.
The minimum and maximum scale range values reported in ArcMap for WMS layers differ from those reported in the service capabilities.
The OGC specifications (version 1.1.1) recommend that minimum and maximum scale range values be based on the ground distance, in meters, between the southwest and northeast diagonal of the central pixel of the map image. This can be significantly different than the value expressed by ArcMap once the WMS layer has been added. However, the scale range used by ArcMap should reflect the general intention of the WMS service author.
The definitions of minimum and maximum used by ArcMap are reversed from what is reported by the service capabilities file (and by ArcCatalog). In ArcMap, the minimum scale is the smallest scale in which a layer will draw. If both minimum and maximum scales are set in ArcMap, the minimum scale will be the larger number.