diff --git a/bwifi.sh b/bwifi.sh
index 00d2329..ca58e45 100755
--- a/bwifi.sh
+++ b/bwifi.sh
@@ -32,7 +32,8 @@ if [ "$auth_host" == *"10.1.206.13"* ] ; then
     username="${username}@bistu"
 fi
 
-# form data
+# Note that the encoding of response is gb2312, so we need to transcode
+# before comparing the title to judge whether we succeed to login.
 title=$(curl --no-progress-meter --include \
             --data-urlencode "DDDDD=$username" \
             --data-urlencode "upass=$password" \