Index: gc_lang/fr/webext/content_scripts/menu.css
==================================================================
--- gc_lang/fr/webext/content_scripts/menu.css
+++ gc_lang/fr/webext/content_scripts/menu.css
@@ -13,11 +13,11 @@
     border-top: 4px solid hsla(210, 100%, 40%, .7);
     border-bottom: 4px solid hsla(210, 100%, 40%, .7);
     border-radius: 50%;
     text-align: center;
     cursor: pointer;
-    z-index: 100000000;
+    z-index: 2147483640; /* maximum is 2147483647: https://stackoverflow.com/questions/491052/minimum-and-maximum-value-of-z-index */
     animation: grammalecte-spin 4s ease infinite;
 }
 .grammalecte_menu_main_button:hover {
     border: 4px solid hsla(210, 80%, 35%, .5);
     background-color: hsla(210, 80%, 55%, .5);
@@ -50,10 +50,11 @@
     border-radius: 5px;
     border: 3px solid hsl(210, 50%, 30%);
     box-shadow: 0px 0px 2px hsla(210, 10%, 10%, .5);
     background-color: hsl(210, 50%, 30%);
     font-family: "Trebuchet MS", "Fira Sans", "Liberation Sans", sans-serif;
+    z-index: 2147483640; /* maximum is 2147483647: https://stackoverflow.com/questions/491052/minimum-and-maximum-value-of-z-index */
 }
 
 .grammalecte_menu_item {
     padding: 3px 10px;
     background-color: hsl(210, 50%, 40%);

Index: gc_lang/fr/webext/content_scripts/panel.css
==================================================================
--- gc_lang/fr/webext/content_scripts/panel.css
+++ gc_lang/fr/webext/content_scripts/panel.css
@@ -6,11 +6,11 @@
 .grammalecte_panel {
     padding: 0;
     margin: 0;
     position: fixed;
     box-sizing: content-box;
-    z-index: 2147483640; /* maximum is 2147483647: https://stackoverflow.com/questions/491052/minimum-and-maximum-value-of-z-index */
+    z-index: 2147483641; /* maximum is 2147483647: https://stackoverflow.com/questions/491052/minimum-and-maximum-value-of-z-index */
     border: 2px solid hsl(210, 10%, 50%);
     border-radius: 10px 10px 10px 10px;
     background-color: hsl(210, 0%, 100%);
     color: hsl(0, 0%, 0%);
     font-family: "Trebuchet MS", "Fira Sans", "Liberation Sans", sans-serif;