diff --git a/assets/css/lesson.scss b/assets/css/lesson.scss
index fe008e501b4f65585309f8297a5d734685bbba2c..abbaecb738f85f74f69134bc3f3d2956faf73570 100644
--- a/assets/css/lesson.scss
+++ b/assets/css/lesson.scss
@@ -153,3 +153,25 @@ span.fold-unfold {
   margin-left: 1em;
   opacity: 0.5;
 }
+
+
+//----------------------------------------
+// keyboard key style, from StackExchange.
+//----------------------------------------
+
+kbd {
+    display: inline-block;
+    margin: 0 .1em;
+    padding: .1em .6em;
+    font-family: Arial,"Helvetica Neue",Helvetica,sans-serif;
+    font-size: 11px;
+    line-height: 1.4;
+    color: #242729;
+    text-shadow: 0 1px 0 #FFF;
+    background-color: #e1e3e5;
+    border: 1px solid #adb3b9;
+    border-radius: 3px;
+    box-shadow: 0 1px 0 rgba(12,13,14,0.2), 0 0 0 2px #FFF inset;
+    white-space: nowrap;
+    font-style: normal;
+}