diff --git a/recipes/002_registration.py b/recipes/002_registration.py
index 3e554714..e36b7f0a 100644
--- a/recipes/002_registration.py
+++ b/recipes/002_registration.py
@@ -110,6 +110,8 @@
       - [Original Paper](Link/to/the/original/paper)
       - [Source Code](Link/to/the/source/code)
 
+Please do not use HTML tags in the README.md file. Only markdown is allowed. For security reasons, the HTML tags will be removed when the package is registered on the web page.
+
 It is highly recommended that you confirm your package works properly (cf. :doc:`005_debugging`) before making a pull request.
 
 Before making a pull request, please ensure the code examples in ``README.md`` and example.py do not contain your local directory and/or your fork of the registry.
diff --git a/template/README.md b/template/README.md
index 2ef91a7a..e2d31d6c 100644
--- a/template/README.md
+++ b/template/README.md
@@ -27,9 +27,11 @@ license: "MIT License"
 ---
 -->
 
-Please read the [tutorial guide](https://optuna.github.io/optunahub-registry/recipes/001_first.html) to register your feature in OptunaHub.
-You can find more detailed explanation of the following contents in the tutorial.
-Looking at [other packages' implementations](https://github.com/optuna/optunahub-registry/tree/main/package) will also help you.
+Instruction (Please remove this instruction after you carefully read)
+
+- Please read the [tutorial guide](https://optuna.github.io/optunahub-registry/recipes/001_first.html) to register your feature in OptunaHub. You can find more detailed explanation of the following contents in the tutorial.
+- Looking at [other packages' implementations](https://github.com/optuna/optunahub-registry/tree/main/package) would also be helpful.
+- **Please do not use HTML tags in the `README.md` file. Only markdown is allowed. For security reasons, the HTML tags will be removed when the package is registered on the web page.**
 
 ## Abstract