Issued following request:
org.vfny.geoserver.WmsException: 3 layers requested, but found 1 styles specified. Since SLD parameter is not yet implemented, the STYLES parameter is mandatory and MUST have exactly one value per requested layer
From the WMS Spec:
A client may request teh default Style using a null value (as in "STYLES="). If several layers are requested with a mixture of named and default styles, the STYLES parameter includes null values between commas (as in "STYLES=style1,,style2,,"). If all layers are to be shown using the default style, either the form "STYLES=" or "STYLES=,,," is valid.