diff --git a/org/w3c/css/parser/analyzer/CssParser.java b/org/w3c/css/parser/analyzer/CssParser.java
index c88f9d08e..a5b090a04 100644
--- a/org/w3c/css/parser/analyzer/CssParser.java
+++ b/org/w3c/css/parser/analyzer/CssParser.java
@@ -2295,13 +2295,25 @@ final public void ignoreStatement() throws ParseException {
  */
   final public void atRuleDeclaration() throws ParseException {Token n;
     n = jj_consume_token(ATKEYWORD);
-//ac.getFrame().addWarning("at-rule", token.toString());
-            ac.getFrame().addError(
-                          new CssError(new InvalidParamException("at-rule",
-                                                                 token, ac)));
+if (n.toString().charAt(1) == '-') {
+                        if (ac.getTreatVendorExtensionsAsWarnings()) {
+                                ac.getFrame() //
+                                        .addWarning("at-rule", //
+                                                n.toString());
+                        } else {
+                                addAtRuleError();
+                        }
+                } else {
+                        addAtRuleError();
+                }
             skipStatement();
   }
 
+  void addAtRuleError() throws ParseException {//
+        ac.getFrame().addError(new CssError(new InvalidParamException( //
+                                "at-rule", token, ac)));
+  }
+
 /**
  * @exception ParseException exception during the parse
  */
@@ -5295,55 +5307,6 @@ private boolean jj_2_5(int xla)
     finally { jj_save(4, xla); }
   }
 
-  private boolean jj_3R_126()
- {
-    if (jj_scan_token(S)) return true;
-    return false;
-  }
-
-  private boolean jj_3R_122()
- {
-    Token xsp;
-    while (true) {
-      xsp = jj_scanpos;
-      if (jj_3R_126()) { jj_scanpos = xsp; break; }
-    }
-    if (jj_scan_token(MINUS)) return true;
-    return false;
-  }
-
-  private boolean jj_3_5()
- {
-    if (jj_3R_125()) return true;
-    if (jj_scan_token(LPARAN)) return true;
-    return false;
-  }
-
-  private boolean jj_3R_130()
- {
-    if (jj_3R_138()) return true;
-    if (jj_3R_129()) return true;
-    return false;
-  }
-
-  private boolean jj_3R_182()
- {
-    if (jj_3R_127()) return true;
-    return false;
-  }
-
-  private boolean jj_3_2()
- {
-    if (jj_scan_token(NUMBER)) return true;
-    Token xsp;
-    while (true) {
-      xsp = jj_scanpos;
-      if (jj_scan_token(21)) { jj_scanpos = xsp; break; }
-    }
-    if (jj_scan_token(DIV)) return true;
-    return false;
-  }
-
   private boolean jj_3R_125()
  {
     if (jj_3R_129()) return true;
@@ -5912,6 +5875,55 @@ private boolean jj_3R_138()
     return false;
   }
 
+  private boolean jj_3R_126()
+ {
+    if (jj_scan_token(S)) return true;
+    return false;
+  }
+
+  private boolean jj_3R_122()
+ {
+    Token xsp;
+    while (true) {
+      xsp = jj_scanpos;
+      if (jj_3R_126()) { jj_scanpos = xsp; break; }
+    }
+    if (jj_scan_token(MINUS)) return true;
+    return false;
+  }
+
+  private boolean jj_3_5()
+ {
+    if (jj_3R_125()) return true;
+    if (jj_scan_token(LPARAN)) return true;
+    return false;
+  }
+
+  private boolean jj_3R_130()
+ {
+    if (jj_3R_138()) return true;
+    if (jj_3R_129()) return true;
+    return false;
+  }
+
+  private boolean jj_3R_182()
+ {
+    if (jj_3R_127()) return true;
+    return false;
+  }
+
+  private boolean jj_3_2()
+ {
+    if (jj_scan_token(NUMBER)) return true;
+    Token xsp;
+    while (true) {
+      xsp = jj_scanpos;
+      if (jj_scan_token(21)) { jj_scanpos = xsp; break; }
+    }
+    if (jj_scan_token(DIV)) return true;
+    return false;
+  }
+
   /** Generated Token Manager. */
   public CssParserTokenManager token_source;
   SimpleCharStream jj_input_stream;
diff --git a/org/w3c/css/parser/analyzer/CssParser.jj b/org/w3c/css/parser/analyzer/CssParser.jj
index 851c2ffd0..2f4606c2b 100644
--- a/org/w3c/css/parser/analyzer/CssParser.jj
+++ b/org/w3c/css/parser/analyzer/CssParser.jj
@@ -1500,14 +1500,27 @@ void atRuleDeclaration() :
 {
     n=<ATKEYWORD>
 	{
-	    //ac.getFrame().addWarning("at-rule", token.toString());
-	    ac.getFrame().addError(
-		          new CssError(new InvalidParamException("at-rule", 
-								 token, ac)));
+		if (n.toString().charAt(1) == '-') {
+			if (ac.getTreatVendorExtensionsAsWarnings()) {
+				ac.getFrame() //
+					.addWarning("at-rule", //
+						n.toString());
+			} else {
+				addAtRuleError();
+			}
+		} else {
+			addAtRuleError();
+		}
 	    skipStatement();
 	}
 }
 
+JAVACODE
+void addAtRuleError() { //
+	ac.getFrame().addError(new CssError(new InvalidParamException( //
+				"at-rule", token, ac)));
+}
+
 /**
  * @exception ParseException exception during the parse
  */
diff --git a/org/w3c/css/util/Messages.properties.en b/org/w3c/css/util/Messages.properties.en
index 62a5a7a4e..077920785 100644
--- a/org/w3c/css/util/Messages.properties.en
+++ b/org/w3c/css/util/Messages.properties.en
@@ -186,6 +186,7 @@ warning.relative: Using relative units gives more robust stylesheets in property
 
 # used by org.w3c.css.css.StyleSheetParser and org.w3c.css.css.StyleSheetXMLParser
 error.at-rule: Unrecognized at-rule %s
+warning.at-rule: Unrecognized at-rule %s
 
 # used by all properties and values
 error.operator: %s is an incorrect operator