--- a/browser/extensions/onboarding/content/onboarding.css
+++ b/browser/extensions/onboarding/content/onboarding.css
@@ -146,23 +146,20 @@
 
 /* Onboarding tour list */
 #onboarding-tour-list {
   margin: 40px 0 0 0;
   padding: 0;
 }
 
 #onboarding-tour-list > li {
-  --padding-inline-start: 49px;
-  --padding-top: 14px;
-  --padding-bottom: 14px;
   list-style: none;
-  padding-inline-start: var(--padding-inline-start);
-  padding-top: var(--padding-top);
-  padding-bottom: var(--padding-bottom);
+  padding-inline-start: 49px;
+  padding-top: 14px;
+  padding-bottom: 14px;
   margin-inline-start: 16px;
   margin-bottom: 9px;
   background-repeat: no-repeat;
   background-position: left 17px top 14px;
   background-size: 20px;
   font-size: 16px;
   cursor: pointer;
 }
@@ -175,28 +172,24 @@
   content: url("img/icons_tour-complete.svg");
   position: relative;
   offset-inline-start: 3px;
   top: -10px;
   float: inline-start;
 }
 
 #onboarding-tour-list > li.onboarding-complete {
-  --padding-inline-start: 29px;
+  padding-inline-start: 29px;
 }
 
 #onboarding-tour-list > li.onboarding-active,
 #onboarding-tour-list > li:hover {
   color: #0A84FF;
-  /* With 1px transparent border, could see a border in the high-constrast mode */
-  border: 1px solid transparent;
-  /* Substract 1px for the 1px transparent or a 1px shift would happen */
-  padding-inline-start: calc(var(--padding-inline-start) - 1px);
-  padding-top: calc(var(--padding-top) - 1px);
-  padding-bottom: calc(var(--padding-bottom) - 1px);
+  /* With 1px transparent outline, could see a border in the high-constrast mode */
+  outline: 1px solid transparent;
 }
 
 /* Default browser tour */
 #onboarding-tour-is-default-browser-msg {
   font-size: 16px;
   line-height: 21px;
   float: inline-end;
   margin-inline-end: 26px;