Fixes #12748

less/type.less

@@ -81,6 +81,12 @@ small,
 // Undo browser default styling
 cite    { font-style: normal; }
 
+mark,
+.mark {
+  background-color: @state-warning-bg;
+  padding: .2em;
+}
+
 // Alignment
 .text-left           { text-align: left; }
 .text-right          { text-align: right; }