diff --git a/browser/base/content/browser.css b/browser/base/content/browser.css
index cdd08ec8f3d3cd652be9fcf6d4fb5b50dcf270ba..6cb35378aea2e7967dff0c91d09201b053645fbd 100644
--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -2,6 +2,8 @@
  * 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/. */
 
+@import url("chrome://global/skin/zen-global-shared.css");
+
 @namespace html url("http://www.w3.org/1999/xhtml");
 
 panelmultiview {
@@ -566,9 +568,9 @@ printpreview-pagination:focus-within,
 
 
 #sidebar-box {
-  min-width: 14em;
+  min-width: 323px;
   max-width: 36em;
-  width: 18em;
+  width: 393px;
 }
 
 /* WebExtension Sidebars */
@@ -583,3 +585,43 @@ printpreview-pagination:focus-within,
 toolbar[keyNav=true]:not([collapsed=true], [customizing=true]) toolbartabstop {
   -moz-user-focus: normal;
 }
+
+
+/**
+ *
+ * ZEN OVERRIDES
+ */
+
+.content-prompt-dialog > .dialogOverlay {
+  align-content: start;
+}
+
+.dialogBox:not(.spotlightBox) {
+  border: 1px solid var(--zen-dialog-border-color);
+}
+
+#window-modal-dialog:not([zen-dialog-welcome-element="true"]) .dialogBox:not(.spotlightBox) {
+  transform: translateY(-9px);
+}
+
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogBox:not(.spotlightBox) {
+  margin: 0 !important;
+}
+
+#window-modal-dialog[zen-dialog-welcome-element="true"], 
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogOverlay,
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogFrame,
+#window-modal-dialog[zen-dialog-welcome-element="true"] .dialogBox {
+  width: 100% !important;
+  height: 100% !important;
+  max-height: none !important;
+  max-width: none !important;
+}
+
+#window-modal-dialog[zen-dialog-welcome-element="true"] {
+  --zen-welcome-dialog-space: 7px;
+  margin: 0 auto !important;
+  max-width: calc(100% - calc(var(--zen-welcome-dialog-space) * 2)) !important;
+  max-height: calc(100% - calc(var(--zen-welcome-dialog-space) * 2)) !important;
+  margin-top: var(--zen-welcome-dialog-space) !important;
+}