diff --git a/browser/extensions/formautofill/skin/shared/editAddress.css b/browser/extensions/formautofill/skin/shared/editAddress.css
index 42b8774fabe1..2717f8b65c8d 100644
--- a/browser/extensions/formautofill/skin/shared/editAddress.css
+++ b/browser/extensions/formautofill/skin/shared/editAddress.css
@@ -43,6 +43,7 @@ select {
 }
 
 #country-warning-message {
+  font-size: 1rem;
   flex: 1 0 auto;
   align-items: center;
   text-align: start;
diff --git a/browser/extensions/formautofill/skin/shared/editCreditCard.css b/browser/extensions/formautofill/skin/shared/editCreditCard.css
index 621cb7cce568..7af65d2cfc67 100644
--- a/browser/extensions/formautofill/skin/shared/editCreditCard.css
+++ b/browser/extensions/formautofill/skin/shared/editCreditCard.css
@@ -10,7 +10,6 @@ form > label,
 form > div {
   flex: 1 0 100%;
   align-self: center;
-  font-size: 1.3em;
   margin: 0 0 0.5em !important;
 }
 
diff --git a/browser/extensions/formautofill/skin/shared/editDialog.css b/browser/extensions/formautofill/skin/shared/editDialog.css
index 2dd29994960b..6fd99ba30729 100644
--- a/browser/extensions/formautofill/skin/shared/editDialog.css
+++ b/browser/extensions/formautofill/skin/shared/editDialog.css
@@ -2,10 +2,6 @@
  * 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,
@@ -42,7 +38,6 @@ textarea {
 }
 
 button {
-  font-size: 1.2em;
   padding: 3px 2em;
   margin-inline-start: 10px;
   margin-inline-end: 0;
diff --git a/browser/themes/linux/preferences/in-content/dialog.css b/browser/themes/linux/preferences/in-content/dialog.css
index 3b1ae45e0fd3..21f6b33dae1f 100644
--- a/browser/themes/linux/preferences/in-content/dialog.css
+++ b/browser/themes/linux/preferences/in-content/dialog.css
@@ -9,7 +9,7 @@ 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
diff --git a/browser/themes/osx/preferences/in-content/dialog.css b/browser/themes/osx/preferences/in-content/dialog.css
index 46a6cb91c577..e1972e341274 100644
--- a/browser/themes/osx/preferences/in-content/dialog.css
+++ b/browser/themes/osx/preferences/in-content/dialog.css
@@ -14,7 +14,7 @@ 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
@@ -23,10 +23,6 @@ textbox.tree-input {
   font-size: unset;
 }
 
-button {
-  font-size: 1em;
-}
-
 caption {
   font: message-box;
 }
diff --git a/browser/themes/windows/preferences/in-content/dialog.css b/browser/themes/windows/preferences/in-content/dialog.css
index 3b1ae45e0fd3..21f6b33dae1f 100644
--- a/browser/themes/windows/preferences/in-content/dialog.css
+++ b/browser/themes/windows/preferences/in-content/dialog.css
@@ -9,7 +9,7 @@ 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
diff --git a/toolkit/themes/linux/global/in-content/common.css b/toolkit/themes/linux/global/in-content/common.css
index 20a20015840d..2c8d1c85c7bd 100644
--- a/toolkit/themes/linux/global/in-content/common.css
+++ b/toolkit/themes/linux/global/in-content/common.css
@@ -131,7 +131,7 @@ xul|window * {
   font-size: 1.19rem;
 }
 
-xul|caption > xul|label {
+xul|caption > xul|label:not(.dialogTitle) {
   font-size: 1.27rem;
 }
 
diff --git a/toolkit/themes/osx/global/in-content/common.css b/toolkit/themes/osx/global/in-content/common.css
index f1e79aea8030..aa80a539bcc9 100644
--- a/toolkit/themes/osx/global/in-content/common.css
+++ b/toolkit/themes/osx/global/in-content/common.css
@@ -143,7 +143,7 @@ xul|window * {
   font-size: 1.45rem;
 }
 
-xul|caption > xul|label {
+xul|caption > xul|label:not(.dialogTitle) {
   font-size: 1.55rem;
 }
 
diff --git a/toolkit/themes/shared/in-content/common.inc.css b/toolkit/themes/shared/in-content/common.inc.css
index 495c5fd1273f..c2216d36f402 100644
--- a/toolkit/themes/shared/in-content/common.inc.css
+++ b/toolkit/themes/shared/in-content/common.inc.css
@@ -893,6 +893,14 @@ xul|treecol:not([hideheader="true"]) > xul|*.treecol-sortdirection[sortDirection
   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;
diff --git a/toolkit/themes/windows/global/in-content/common.css b/toolkit/themes/windows/global/in-content/common.css
index 59dce5fa2802..3a8983b26593 100644
--- a/toolkit/themes/windows/global/in-content/common.css
+++ b/toolkit/themes/windows/global/in-content/common.css
@@ -92,7 +92,7 @@ xul|window * {
   font-size: 1.33rem;
 }
 
-xul|caption > xul|label {
+xul|caption > xul|label:not(.dialogTitle) {
   font-size: 1.42rem;
 }