diff --git a/poul/css/poul.css b/poul/css/poul.css
index f70553d8dbe16d4270b943ea95da32bd29ce6ba9..d3b58bc41120d3466676dc10956b565995fa4c56 100644
--- a/poul/css/poul.css
+++ b/poul/css/poul.css
@@ -274,6 +274,23 @@ body {
     vertical-align: top;
 }
 
+.reveal .warning {
+    display: flex;
+    background-color: #ff464b;
+    border-radius: 10px;
+    width: 100%;
+    padding: 10px 10px 10px 100px;
+    min-height: 75px;
+    background-size: 100px 90%;
+    background-position: 10px;
+    background-repeat: no-repeat;
+    flex-direction: column;
+    align-content: center;
+    justify-content: center;
+    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 486.46 486.46' xml:space='preserve' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath fill='%23fff' d='M243.32 20.883c-31.4 0-59.398 16.298-74.898 43.398l-156.8 271.5c-15.6 27.3-15.499 59.8.3 86.9 15.6 26.8 43.5 42.9 74.7 42.9h312.8c31.3 0 59.399-16.3 75.199-43.6 15.7-27.1 15.799-59.4.199-86.4l-156.6-271.2c-15.5-27.3-43.5-43.5-74.9-43.5zm0 39.199c17.1 0 32.4 8.9 40.9 23.801l156.7 271.4c8.4 14.6 8.3 32.202-.3 47.102-8.7 15-24.102 23.898-41.302 23.898h-312.8c-17 0-32.3-8.698-40.8-23.398-8.6-14.9-8.7-32.701-.1-47.701l156.8-271.4c8.5-14.9 23.698-23.699 40.898-23.699zm.35 97.102a26.237 26.237 0 0 0-6.649.7c-11.9 3.4-19.3 14.198-19.3 27.298.6 7.9 1.1 15.901 1.7 23.801 1.7 30.1 3.4 59.6 5.1 89.7.6 10.2 8.5 17.6 18.699 17.6s18.201-7.9 18.701-18.2c0-6.2 0-11.899.6-18.199 1.1-19.3 2.3-38.6 3.4-57.9.6-12.5 1.699-25 2.299-37.5 0-4.5-.599-8.5-2.299-12.5-4.144-9.1-12.777-14.57-22.252-14.799zm-.45 176.2c-13.6 0-25 11.4-25 25s11.4 25 25 25c13.1 0 25-11.4 24.4-24.4.6-14.3-10.7-25.6-24.4-25.6z'/%3E%3C/svg%3E%0A");
+    content: " ";
+}
+
 /*********************************************
  * LINKS
  *********************************************/
@@ -410,4 +427,4 @@ body {
 
 .reveal code.input.root::before, .reveal pre.input.root > code::before {
     content: "#";
-}
\ No newline at end of file
+}
diff --git a/slides/content.md b/slides/content.md
index ec121742c1e22239001451e74909dba646999d8f..8d02a20f5151fa0e97abe1afb5fbccc8c9e67079 100644
--- a/slides/content.md
+++ b/slides/content.md
@@ -52,6 +52,12 @@ finally:
 
 ----
 
+### How to display a warning
+
+This is a warning box <!-- .element: class="warning" -->
+
+----
+
 - Do you remember bullet list?
   ```python
   bullet_list = ["Do you remember bullet list?"]
@@ -64,4 +70,4 @@ finally:
   ```python
   if not hard:
       bullet_list.append("It's not too hard!")
-  ```
\ No newline at end of file
+  ```