diff --git a/web/grab_to_pan.js b/web/grab_to_pan.js
index 99071a41b..8458f087d 100644
--- a/web/grab_to_pan.js
+++ b/web/grab_to_pan.js
@@ -180,7 +180,7 @@ GrabToPan.prototype = {
 
 // Get the correct (vendor-prefixed) name of the matches method.
 let matchesSelector;
-["webkitM", "mozM", "oM", "m"].some(function (prefix) {
+["webkitM", "mozM", "m"].some(function (prefix) {
   let name = prefix + "atches";
   if (name in document.documentElement) {
     matchesSelector = name;
diff --git a/web/ui_utils.js b/web/ui_utils.js
index f547fdd87..d08497165 100644
--- a/web/ui_utils.js
+++ b/web/ui_utils.js
@@ -99,7 +99,6 @@ function getOutputScale(ctx) {
   const backingStoreRatio =
     ctx.webkitBackingStorePixelRatio ||
     ctx.mozBackingStorePixelRatio ||
-    ctx.oBackingStorePixelRatio ||
     ctx.backingStorePixelRatio ||
     1;
   const pixelRatio = devicePixelRatio / backingStoreRatio;
diff --git a/web/viewer.css b/web/viewer.css
index 72f82ff1e..18c3d7828 100644
--- a/web/viewer.css
+++ b/web/viewer.css
@@ -829,7 +829,6 @@ html[dir="rtl"] .splitToolbarButtonSeparator {
   font-size: 12px;
   line-height: 14px;
   user-select: none;
-  /* Opera does not support user-select, use <... unselectable="on"> instead */
   cursor: default;
   box-sizing: border-box;
 }