tweak error message

errors.php

@@ -27,6 +27,5 @@
 	$ERRORS[10] = __("Your version of MySQL is not currently supported. Please see 
 		official site for more information.");
 
-	$ERRORS[11] = __("Sanity check request received twice. You could be running
-		Firebug or some other disrupting extension. Please turn it off.");
+	$ERRORS[11] = "[This error is not returned by server]";
 ?>

prefs.js

@@ -1243,8 +1243,9 @@ function backend_sanity_check_callback() {
 		try {
 
 			if (sanity_check_done) {
-				fatalError(11, "Sanity check request received twice. You could be running"+
-			      " Firebug or some other disrupting extension. Please turn it off.");
+				fatalError(11, "Sanity check request received twice. This can indicate "+
+			      "presence of Firebug or some other disrupting extension. "+
+					"Please disable it and try again.");
 				return;
 			}
 

tt-rss.js

@@ -91,8 +91,9 @@ function backend_sanity_check_callback() {
 		try {
 	
 			if (sanity_check_done) {
-				fatalError(11, "Sanity check request received twice. You could be running"+
-			      " Firebug or some other disrupting extension. Please turn it off.");
+				fatalError(11, "Sanity check request received twice. This can indicate "+
+			      "presence of Firebug or some other disrupting extension. "+
+					"Please disable it and try again.");
 				return;
 			}