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The 'X' symbol has been used since Netscape to stop HTML download. Today, webpages don't load - they show up within milliseconds, provided that JavaScript trackers are disabled. Consider remapping your 'X' to regain visibility and usability.

Main Usage: with Vertical Tabs.
Do you struggle with interpreting the favicons, ellipses and X's of many open tabs? Use this extension with vertical tabs enabled. See userChrome.xml settings under Details.

Culprit for Wasted Space: Desktop Environment Integration.
The X is used for closing the application window, and thus all tabs. Use this extension with a minimize button extension to reclaim unneeded window control X button.

This addon: a temporary solution.
Development must continue probably both on Firefox and on each desktop environment to allow the native window control icons to close vertical tabs in apps.

Credits.
FF addon by [Piradix](https://addons.mozilla.org/en-US/firefox/user/13155612/)
Icon by [13156782](https://addons.mozilla.org/en-US/firefox/addon/tab-close-webext/)

Комментарии разработчика

[file://~/.mozilla/firefox/*/chrome/userChrome.css]
#main-window[tabsintitlebar="false"]:not([extradragspace="true"]) #TabsToolbar > .toolbar-items {
opacity: 0;
pointer-events: none;
}
#main-window:not([tabsintitlebar="false"]) #TabsToolbar {
visibility: collapse !important;
}

#sidebar {
max-width: 800px !important;
min-width: 50px !important;
}

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */
#content browser { margin-right:-14px!important; overflow-y:scroll; overflow-x:hidden;}

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