Chris told me he has a web map service (version 1.3.0), the prefix is: http://gis20.exp.sis.pitt.edu:8080/mapServer/servlet/InOut? Then I know how to access it. First thing is to get the capabilities of this web map service:
http://gis20.exp.sis.pitt.edu:8080/mapServer/servlet/InOut? &version=1.3.0&service=wms&request=GetCapabilitiesClick
After reading the returned XML file, I know how to get map from this service. For example, this is a URL I can use:
http://gis20.exp.sis.pitt.edu:8080/mapServer/servlet/InOut? &version=1.3.0&service=wms&request=GetMap &width=500 &height=250 &format=image/png &crs=crs:83 &bbox=-79.9668355485,40.4390998992,-79.9476867983,40.4484870713 &layers=Backdrop,Buildings, &styles=0x000000,0x00aaff,Click
http://gis20.exp.sis.pitt.edu:8080/mapServer/servlet/InOut? &version=1.3.0&service=wms &request=GetMap &width=800 &height=400 &format=image/png &crs=crs:83 &bbox=-79.9668355485,40.4390998992,-79.9476867983,40.4484870713 &layers=Backdrop,Buildings, &styles=0x000000,0xff0000,Click
You can modify the parameters and input your own URL here, and click "Request URL".
Now I tell you there is another Web Map Service at http://deli.dnr.state.mn.us/cgi-bin/wms?map=DELI_WMS_MAPFILE, and the version is 1.1.1, how can you access this service? You can use the above input box to input your own url and try it!
http://deli.dnr.state.mn.us/cgi-bin/wms?map=DELI_WMS_MAPFILE &service=wms&version=1.1.1&request=GetCapabilitiesClick
You need to save it as a xml file, then view it with web browser or text editor. To make it simple, I save it here.
http://deli.dnr.state.mn.us/cgi-bin/wms?map=DELI_WMS_MAPFILE &version=1.1.1&service=wms&request=GetMap &layers=L390003782306 &width=800&height=600 &format=jpeg &bbox=400000,5000000,401000,5001000Click
Now try it with other layers and other bounding box.
http://deli.dnr.state.mn.us/cgi-bin/wms?service=wms&map=DELI_WMS_MAPFILE&version=1.1.1&request=GetMap&layers=L390003782306,L390002400906&width=800&height=600&format=png&bbox=400000,5000000,401000,5001000