--- a/browser/extensions/formautofill/skin/shared/editAddress.css
+++ b/browser/extensions/formautofill/skin/shared/editAddress.css
@@ -38,14 +38,15 @@ select {
 }
 
 #street-address,
 #email {
   flex: 1 0 auto;
 }
 
 #country-warning-message {
+  font-size: 1rem;
   flex: 1 0 auto;
   align-items: center;
   text-align: start;
   color: #737373;
   padding-inline-start: 1em;
 }

--- a/browser/extensions/formautofill/skin/shared/editCreditCard.css
+++ b/browser/extensions/formautofill/skin/shared/editCreditCard.css
@@ -5,17 +5,16 @@
 form {
   justify-content: center;
 }
 
 form > label,
 form > div {
   flex: 1 0 100%;
   align-self: center;
-  font-size: 1.3em;
   margin: 0 0 0.5em !important;
 }
 
 select {
   flex: 0 0 5em;
   margin: 0;
   margin-inline-end: 0.7em;
 }

--- a/browser/extensions/formautofill/skin/shared/editDialog.css
+++ b/browser/extensions/formautofill/skin/shared/editDialog.css
@@ -1,16 +1,12 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-body {
-  font-size: 1rem;
-}
-
 form,
 label,
 div,
 p {
   display: flex;
 }
 
 form {
@@ -37,17 +33,16 @@ option {
   padding: 0.3em 0.5em;
 }
 
 textarea {
   resize: none;
 }
 
 button {
-  font-size: 1.2em;
   padding: 3px 2em;
   margin-inline-start: 10px;
   margin-inline-end: 0;
 }
 
 input,
 select {
   box-sizing: border-box;

--- a/browser/themes/linux/preferences/in-content/dialog.css
+++ b/browser/themes/linux/preferences/in-content/dialog.css
@@ -4,16 +4,16 @@
 
 %include ../../../shared/incontentprefs/dialog.inc.css
 
 label:not(.menu-text),
 textbox,
 description,
 .tab-text,
 caption > label {
-  font-size: 1.2em;
+  font-size: 1.2rem;
 }
 
 /* Create a separate rule to unset these styles on .tree-input instead of
    using :not(.tree-input) so the selector specifity doesn't change. */
 textbox.tree-input {
   font-size: unset;
 }

--- a/browser/themes/osx/preferences/in-content/dialog.css
+++ b/browser/themes/osx/preferences/in-content/dialog.css
@@ -9,28 +9,24 @@ prefwindow,
   font: message-box !important;
 }
 
 label:not(.menu-text),
 textbox,
 description,
 .tab-text,
 caption > label {
-  font-size: 1.3em;
+  font-size: 1.3rem;
 }
 
 /* Create a separate rule to unset these styles on .tree-input instead of
    using :not(.tree-input) so the selector specifity doesn't change. */
 textbox.tree-input {
   font-size: unset;
 }
 
-button {
-  font-size: 1em;
-}
-
 caption {
   font: message-box;
 }
 
 .prefWindow-dlgbuttons {
   margin: 0;
 }

--- a/browser/themes/windows/preferences/in-content/dialog.css
+++ b/browser/themes/windows/preferences/in-content/dialog.css
@@ -4,16 +4,16 @@
 
 %include ../../../shared/incontentprefs/dialog.inc.css
 
 label:not(.menu-text),
 textbox,
 description,
 .tab-text,
 caption > label {
-  font-size: 1.2em;
+  font-size: 1.2rem;
 }
 
 /* Create a separate rule to unset these styles on .tree-input instead of
    using :not(.tree-input) so the selector specifity doesn't change. */
 textbox.tree-input {
   font-size: unset;
 }

--- a/toolkit/themes/linux/global/in-content/common.css
+++ b/toolkit/themes/linux/global/in-content/common.css
@@ -126,16 +126,16 @@ xul|window * {
 *|*.header-name {
   font-size: 1.64rem;
 }
 
 *|*.category-name {
   font-size: 1.19rem;
 }
 
-xul|caption > xul|label {
+xul|caption > xul|label:not(.dialogTitle) {
   font-size: 1.27rem;
 }
 
 .tip-caption,
 .help-button {
   font-size: 1rem;
 }

--- a/toolkit/themes/osx/global/in-content/common.css
+++ b/toolkit/themes/osx/global/in-content/common.css
@@ -138,16 +138,16 @@ xul|window * {
 *|*.header-name {
   font-size: 2rem;
 }
 
 *|*.category-name {
   font-size: 1.45rem;
 }
 
-xul|caption > xul|label {
+xul|caption > xul|label:not(.dialogTitle) {
   font-size: 1.55rem;
 }
 
 .tip-caption,
 .help-button {
   font-size: 1.18rem;
 }

--- a/toolkit/themes/shared/in-content/common.inc.css
+++ b/toolkit/themes/shared/in-content/common.inc.css
@@ -888,16 +888,24 @@ xul|treecol:not([hideheader="true"]) > x
   width: 18px;
   height: 18px;
 }
 
 xul|treecol:not([hideheader="true"]) > xul|*.treecol-sortdirection[sortDirection="ascending"] {
   transform: scaleY(-1);
 }
 
+xul|treecol > xul|label.treecol-text {
+  font-size: 1rem;
+}
+
+xul|treechildren {
+  font-size: 1rem !important;
+}
+
 /* This is the only way to increase the height of a tree row unfortunately */
 xul|treechildren::-moz-tree-row {
   min-height: 2em;
 }
 
 /* Color needs to be set on tree cell in order to be applied */
 xul|treechildren::-moz-tree-cell-text {
   color: var(--in-content-text-color);

--- a/toolkit/themes/windows/global/in-content/common.css
+++ b/toolkit/themes/windows/global/in-content/common.css
@@ -87,16 +87,16 @@ xul|window * {
 *|*.header-name {
   font-size: 1.83rem;
 }
 
 *|*.category-name {
   font-size: 1.33rem;
 }
 
-xul|caption > xul|label {
+xul|caption > xul|label:not(.dialogTitle) {
   font-size: 1.42rem;
 }
 
 .tip-caption,
 .help-button {
   font-size: 1.08rem;
 }