diff --git a/lib/sso_login_box/login_tag.rb b/lib/sso_login_box/login_tag.rb
index 48ea151..3dd3615 100644
--- a/lib/sso_login_box/login_tag.rb
+++ b/lib/sso_login_box/login_tag.rb
@@ -1,8 +1,13 @@
 module SsoLoginBox::LoginTag
   def self.show
-    "<div class=\"pull-right\">
+    "<style type=\"text/css\">
+      a.sso_login_button:focus {
+          outline: 0 !important;
+      }
+    </style>
+    <div class=\"pull-right\">
       <button class=\"login-btn\">
-        <a href=\"https://api.ntnu.edu.tw/NtnuCloud/auth?response_type=#{ENV['RESPONSE_TYPE']}&client_id=#{ENV['APP_ID']}&redirect_uri=#{ENV['REDIRECT_URI']}\">
+        <a class=\"sso_login_button\" href=\"https://api.ntnu.edu.tw/NtnuCloud/auth?response_type=#{ENV['RESPONSE_TYPE']}&client_id=#{ENV['APP_ID']}&redirect_uri=#{ENV['REDIRECT_URI']}\">
           NTNU SSO Login
         </a>
       </button>