Change impression count to exclude when :referrer is nil

app/helpers/application_helper.rb

@@ -181,7 +181,7 @@ module ApplicationHelper
   end
 
   def display_visitors(options={})
-    Impression.where(options).distinct(:session_hash).count
+    Impression.where(options).and(:referrer.ne => nil).distinct(:session_hash).count
   end
 
   def display_visitors_today