This was a major change for WMS Server support in MapServer 5.0. MapServer WMS Server GetMap requests now require the following additional parameters:

• srs
• bbox
• width
• height
• format
• styles

Note that these parameters were always required in all versions of the WMS specification, but MapServer previously had not required them in a client request (even though most OGC WMS clients would issue them anyway to be consistent with the WMS spec).

The request below now constitutes a valid GetMap request:

http://wms.example.com/wms?service=WMS&version=1.1.1&request=GetMap&layers=foo&srs=EPSG:4326&bbox=-180,-90,180,90&format=image/png&width=400&height=300&styles=default

Which is consistent with the WMS specification.

More information on these parameters can be found in the WMS Server howto and the OGC WMS 1.1.1 specification

For more detailed information, see ticket 1088

UPDATE: STYLES, though a required WMS parameter, is now optional again in MapServer. For more detailed inforamation, see ticket 2427