there was a post [https://support.mozilla.org/en-US/que.../1274416?page=2|here]

when it changed to 71. the "fix" for 72 is to move the @namespace to after the tabs section.

however, doing that i no longer have text on my tabs for the pages with long titles, and the close tab "X" is no longer on the upper right corner of the tab.

Hi boshk11

What other code do you have in userChrome.css ?

Removing the @namespace shouldn't have that much effect.

Can you post your userChrome.css code ?

Do you have a @-moz-document in your userChrome.css file?

@-moz-document url(chrome://browser/content/browser.xul) =>
@-moz-document url(chrome://browser/content/browser.xhtml)

i literally only use chrome.css for tabs on bottom. i copied the code (below) posted when firefox 71 came out to fix the issue. if you do not remove or move the @namespace the tabs bar overlaps with the bookmarks bar. moving @namespace to the bottom after the tabs or removing it causes the tabs to come back, but if the page title is too long it moves down below the page icon

/* TABS: on bottom */

1. navigator-toolbox toolbar:not(#nav-bar):not(#toolbar-menubar) {-moz-box-ordinal-group:10}
2. TabsToolbar {-moz-box-ordinal-group:1000!important}

1. TabsToolbar {

display: block !important; /*required for 71+*/
position: absolute !important;
bottom: 0 !important;
width: 100vw !important;

}

1. tabbrowser-tabs {

 width: 100vw !important;

}

1. main-window:not([chromehidden*="toolbar"]) #navigator-toolbox {padding-bottom: var(--tab-min-height) !important;}

/* TABS: height */

root {

--tab-toolbar-navbar-overlap: 0px !important;
--tab-min-height: 27px !important; /* adjust to suit your needs */

}

root #tabbrowser-tabs {

--tab-min-height: 27px !important; /* needs to be the same as above under :root */
--tab-min-width: 80px !important;

}

1. TabsToolbar {

height: var(--tab-min-height) !important;
margin-bottom: 1px !important;
box-shadow: ThreeDShadow 0 -1px inset, -moz-dialog 0 1px !important;

}

1. tabbrowser-tabs,
2. tabbrowser-tabs > .tabbrowser-arrowscrollbox,

.tabbrowser-tabs[positionpinnedtabs] > .tabbrowser-tab[pinned] {

 min-height: var(--tab-min-height) !important;
 max-height: var(--tab-min-height) !important;

}

/* drag space */ .titlebar-spacer[type="pre-tabs"], .titlebar-spacer[type="post-tabs"] {

 width: 40px;

}

/* Override vertical shifts when moving a tab */

1. navigator-toolbox[movingtab] > #titlebar > #TabsToolbar {

 padding-bottom: unset !important;

}

1. navigator-toolbox[movingtab] #tabbrowser-tabs {

 padding-bottom: unset !important;
 margin-bottom: unset !important;

}

1. navigator-toolbox[movingtab] > #nav-bar {

 margin-top: unset !important;

}

/* Colored bookmark sidebar, toolbar, menu button containers */

 /* Standard folder */
 #bookmarks-view treechildren::-moz-tree-image(container),
 #PlacesToolbarItems toolbarbutton[container="true"] .toolbarbutton-icon,
 #PlacesToolbarItems menu[container="true"] .menu-iconic-left,
 #BMB_bookmarksPopup menu[container="true"] .menu-iconic-icon {
   fill: gold !important;
 }
 /* Live Bookmark (RSS Feed) */
 #bookmarks-view treechildren::-moz-tree-image(container, livemark),
 #PlacesToolbarItems toolbarbutton[container="true"][livemark="true"] .toolbarbutton-icon,
 #PlacesToolbarItems menu[container="true"][livemark="true"] .menu-iconic-left,
 #BMB_bookmarksPopup menu[container="true"][livemark="true"] .menu-iconic-icon {
   fill: orange !important;
 }
 /* Smart bookmark folder */
 #bookmarks-view treechildren::-moz-tree-image(container, query),
 #PlacesToolbarItems toolbarbutton[container="true"][query="true"] .toolbarbutton-icon,
 #PlacesToolbarItems menu[container="true"][query="true"] .menu-iconic-left,
 #BMB_bookmarksPopup menu[container="true"][query="true"] .menu-iconic-icon {
   fill: dimtan !important;
 }
 /* These "containers" are SVG in the sidebar, not yet on the menu */
 #bookmarks-view treechildren::-moz-tree-image(container, OrganizerQuery_BookmarksMenu) {
   fill: tan !important;
 }
 #bookmarks-view treechildren::-moz-tree-image(container, OrganizerQuery_BookmarksToolbar) {
   fill: tan !important;
 }
 #bookmarks-view treechildren::-moz-tree-image(container, OrganizerQuery_UnfiledBookmarks) {
   fill: tan !important;
 }

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */