diff --git a/userContent.css b/userContent.css
index 21be914..376e66b 100644
--- a/userContent.css
+++ b/userContent.css
@@ -120,6 +120,7 @@
 
   /** Fully Dark Mode *********************************************************/
   /*= Fully Dark Mode - Dark Mode Colors =====================================*/
+  /* Based on chrome://global/skin/in-content/common.css */
   :host,
   :root {
     --in-content-page-color: rgb(21, 20, 26);
@@ -278,13 +279,18 @@
 
   /*= Fully Dark Mode - abouts' common =======================================*/
     @-moz-document url-prefix("about:plugins"),
-                   url-prefix("about:cache") {
+                   url-prefix("about:cache"),
+                   url-prefix("about:checkerboard") {
+      /* Base */
+      :root {
+        font: message-box !important;
+        appearance: none !important;
+      }
       :root,
       body {
         background-color: var(--in-content-page-background) !important;
         color: var(--in-content-page-color) !important;
       }
-
       body {
         font-size: 15px !important;
         font-weight: normal !important;
@@ -298,10 +304,186 @@
         line-height: 1.4em !important;
       }
 
+      /* Link */
       a {
         color: var(--in-content-link-color) !important;
       }
+      a:hover,
+      .text-link:hover {
+        color: var(--in-content-link-color-hover) !important;
+        text-decoration: underline !important;
+      }
+      a:visited {
+        color: var(--in-content-link-color-visited) !important;
+      }
+      a:hover:active,
+      .text-link:hover:active {
+        color: var(--in-content-link-color-active) !important;
+      }
+      a:-moz-focusring,
+      .text-link:-moz-focusring {
+        outline: 2px solid var(--in-content-focus-outline-color) !important;
+        outline-offset: 1px !important;
+        border-radius: 4px !important;
+      }
 
+      /* Button */
+      button {
+        font: inherit;
+      }
+      button,
+      select,
+      input[type="color"] {
+        appearance: none !important;
+        min-height: 32px !important;
+        color: var(--in-content-button-text-color, inherit) !important;
+        border: 1px solid transparent !important; /* shows up in high-contrast mode */
+        border-radius: var(--in-content-button-border-radius) !important;
+        background-color: var(--in-content-button-background) !important;
+        font-weight: 400 !important;
+        padding: var(--in-content-button-vertical-padding) var(--in-content-button-horizontal-padding) !important;
+        text-decoration: none !important;
+        margin: 4px 8px !important;
+        /* Ensure font-size isn't overridden by widget styling (e.g. in forms.css) */
+        font-size: 1em !important;
+      }
+      button {
+        font-weight: 600 !important;
+        /* Use the same margin of other elements for the alignment */
+        margin-inline: 4px !important;
+        min-width: 6.3em !important;
+      }
+      /* Medium and small buttons get sized to 7/14 and 6/12px padding (when adding
+       * the 1px border): */
+      button.medium {
+        --in-content-button-vertical-padding: 6px;
+        --in-content-button-horizontal-padding: 13px;
+        min-height: 28px !important;
+        font-size: 0.95em !important;
+      }
+      button.small {
+        --in-content-button-vertical-padding: 5px;
+        --in-content-button-horizontal-padding: 11px;
+        min-height: 24px !important;
+        font-size: 0.9em !important;
+      }
+      ::-moz-focus-inner {
+        border: none !important;
+      }
+      button:-moz-focusring {
+        box-shadow: none !important;
+        outline: 2px solid var(--in-content-focus-outline-color) !important;
+        outline-offset: 2px !important;
+      }
+      button:enabled:hover,
+      input[type="color"]:hover {
+        background-color: var(--in-content-button-background-hover) !important;
+        color: var(--in-content-button-text-color-hover) !important;
+        border-color: transparent !important;
+      }
+      button:enabled:hover:active,
+      input[type="color"]:enabled:hover:active {
+        background-color: var(--in-content-button-background-active) !important;
+      }
+      button:disabled,
+      input[type="color"]:disabled {
+        opacity: 0.4 !important;
+      }
+      button[autofocus],
+      button[type="submit"],
+      button.primary {
+        background-color: var(--in-content-primary-button-background) !important;
+        color: var(--in-content-primary-button-text-color) !important;
+      }
+      button[autofocus]:enabled:hover,
+      button[type="submit"]:enabled:hover,
+      button.primary:enabled:hover {
+        background-color: var(--in-content-primary-button-background-hover) !important;
+        color: var(--in-content-primary-button-text-color-hover) !important;
+      }
+      button[autofocus]:enabled:hover:active,
+      button[type="submit"]:enabled:hover:active,
+      button.primary:enabled:hover:active {
+        background-color: var(--in-content-primary-button-background-active) !important;
+      }
+
+      /* Checkbox */
+      input[type="checkbox"] {
+        margin-block: 2px !important;
+      }
+      input[type="checkbox"] {
+        appearance: none !important;
+        height: 16px !important;
+        width:  16px !important;
+        border: 1px solid var(--checkbox-border-color) !important;
+        background-color: var(--checkbox-unchecked-bgcolor) !important;
+        border-radius: 2px !important;
+        margin-inline: 0 6px !important;
+        flex-shrink: 0 !important; /* avoid shrinking inside flex container */
+      }
+      input[type="checkbox"]:enabled:hover {
+        background-color: var(--checkbox-unchecked-hover-bgcolor) !important;
+      }
+      input[type="checkbox"]:enabled:hover:active {
+        background-color: var(--checkbox-unchecked-active-bgcolor) !important;
+      }
+      input[type="checkbox"]:checked {
+        border-color: var(--checkbox-checked-border-color) !important;
+        background-color: var(--checkbox-checked-bgcolor) !important;
+        background-image: url("chrome://global/skin/icons/check.svg") !important;
+        background-position: center !important;
+        background-repeat: no-repeat !important;
+        -moz-context-properties: fill !important;
+        fill: currentColor !important;
+        color: var(--checkbox-checked-color) !important;
+        /* Style the button also when printing with "Print Backgrounds" unchecked */
+        color-adjust: exact !important;
+      }
+      input[type="checkbox"]:enabled:checked:hover {
+        background-color: var(--checkbox-checked-hover-bgcolor) !important;
+      }
+      input[type="checkbox"]:enabled:checked:hover:active {
+        background-color: var(--checkbox-checked-active-bgcolor) !important;
+      }
+
+      /* Textarea */
+      input:is([type="email"], [type="tel"], [type="text"], [type="password"], [type="url"], [type="number"]),
+      textarea {
+        appearance: none !important;
+        border: 1px solid var(--in-content-box-border-color) !important;
+        border-radius: 4px !important;
+        color: inherit !important;
+        background-color: var(--in-content-box-background) !important;
+      }
+      input:is([type="email"], [type="tel"], [type="text"], [type="password"], [type="url"], [type="number"]),
+      textarea {
+        font-family: inherit !important;
+        font-size: inherit !important;
+        padding: 8px !important;
+        margin: 2px 4px !important;
+      }
+      input:is([type="email"], [type="tel"], [type="text"], [type="password"], [type="url"], [type="number"]):focus,
+      textarea:focus,
+      search-textbox[focused],
+      tree:focus-visible,
+      richlistbox:focus-visible {
+        border-color: transparent !important;
+        outline: 2px solid var(--in-content-focus-outline-color) !important;
+        outline-offset: -1px !important; /* Prevents antialising around the corners */
+      }
+      input:is([type="email"], [type="tel"], [type="text"], [type="password"], [type="url"], [type="number"]):-moz-ui-invalid,
+      textarea:-moz-ui-invalid {
+        border-color: transparent !important;
+        outline: 2px solid var(--in-content-border-invalid) !important;
+        outline-offset: -1px !important; /* Prevents antialising around the corners */
+      }
+      input:is([type="email"], [type="tel"], [type="text"], [type="password"], [type="url"], [type="number"]):disabled,
+      textarea:disabled,
+      search-textbox[disabled="true"] {
+        opacity: 0.4 !important;
+      }
+
+      /* Table */
       table {
         width: 100% !important;
         border: 1px solid var(--in-content-border-color) !important;
@@ -309,6 +491,16 @@
       }
     }
 
+    @-moz-document url-prefix("about:cache"),
+                   url-prefix("about:checkerboard") {
+      th, td {
+        border: 1px solid var(--in-content-border-color) !important;
+      }
+      th {
+        background-color: var(--in-content-table-header-background) !important;
+        color: var(--in-content-table-header-color) !important;
+      }
+    }
   /*= Fully Dark Mode - about:plugins ========================================*/
     @-moz-document url-prefix("about:plugins") {
       .notice {
@@ -324,14 +516,17 @@
       }
 
       th, td {
-        border: 1px solid var(--in-content-border-color);
-        padding: 4px;
-        text-align: match-parent;
+        padding: 4px !important;
+        text-align: match-parent !important;
       }
+    }
 
-      th {
-        background-color: var(--in-content-table-header-background) !important;
-        color: var(--in-content-table-header-color) !important;
+    @-moz-document url-prefix("about:checkerboard") {
+      #canvas {
+        border: 1px solid var(--in-content-border-color) !important;
+      }
+      #excludePageFromZoom {
+        vertical-align: bottom !important;
       }
     }