Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj	(revision 9335)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj	(revision 9336)
@@ -7,4 +7,6 @@
 PARSER_BEGIN(MapCSSParser)
 package org.openstreetmap.josm.gui.mappaint.mapcss.parsergen;
+
+import static org.openstreetmap.josm.tools.I18n.tr;
 
 import java.io.InputStream;
@@ -381,4 +383,12 @@
 }
 {
+    {
+        if (sheet != null) {
+            String msg = tr("Detected deprecated ''{0}'' in ''{1}'' which will be removed shortly. Use ''{2}'' instead.",
+                            "@media", sheet.getDisplayString(), "@supports");
+            Main.error(msg);
+            sheet.logWarning(msg);
+        }
+    }
     <PP_MEDIA> pp_w()
     ( q=pp_media_query() { pass = pass || q; empty = false; }