diff --git a/web/markdown/markdown.css b/web/markdown/markdown.css
--- a/web/markdown/markdown.css
+++ b/web/markdown/markdown.css
@@ -81,6 +81,11 @@
   background: #33332c;
   color: #33332c;
   cursor: pointer;
+  -webkit-touch-callout: none; /* iOS Safari */
+  -webkit-user-select: none; /* Safari */
+  -moz-user-select: none; /* Old versions of Firefox */
+  -ms-user-select: none; /* Internet Explorer/Edge */
+  user-select: none; /* Non-prefixed version, currently supported by Chrome, Edge, Opera and Firefox */
 }
 span.revealSpoilerAnimation {
   animation: revealSpoiler 1s;