Firefox 151 Breakages

[ChasCB]

Various menu breakages.

It is ONLY affecting; (click links to see images)

(#PlacesToolbarItems menuitem)
#PlacesChevronPopup menu
and all sub-menus within #PlacesChevronPopup
#appMenu
and all sub-menus within #appMenu.

AND, the sub-menus within #appMenu now have a mandatory height as opposed to a flex height.
https://i.ibb.co/WWsHVhhT/Screenshot-2026-05-21-at-17-44-37.png

I have partially solved this with the appMenu.

#appMenu-popup > panelmultiview toolbarbutton,
#appMenu-popup .panel-subview-body,
#appMenu-zoom-controls {
padding-block: 1px !important; /* vertical padding /
margin-inline: 1px !important; / general padding /
padding-block: 1px !important; / vertical padding */
background-color: #D1D1D1 !important;
}

[ChasCB]

Problem solved with the help of those in reddit.com

--panel-menuitem-padding: 0px 5px !important;
    --panel-menuitem-margin: 0px 5px !important;

[ChasCB]

It appears that all the --arrowpanel-variable names have been shortened to just --panel- and the [type=arrow] has gone as well.
I have cleaned up MY own CSS code files from Aris to reflect this.

[TroudhuK]

Thank you for sharing this.
We will cry again soon: https://blog.mozilla.org/en/firefox/new-firefox-design/

[ChasCB]

I am crying already. This current system purple/mauve is just Yuk. Watching the animation video in the above link demonstrates we can customise the default system theme colours, at some point, can not wait.

[ChasCB]

Found the answer

about:config > browser.nova.enabled > change the value to false

[ChasCB]

Aris-t2 urlbar_restore_visible_border.css stopped working for me and after much mucking around and some help from TraditionalTie4831 in reddit I have it working again.

From this:

To this:

NEW code"

root {
    
    --toolbar-field-border-color: #008000 !important;
    --toolbar-field-focus-border-color: #008000 !important;
}

.urlbar[breakout][breakout-extend] {
    box-shadow: inset 0 0 0 1px #008000 !important;
    border: 2px solid #008000 !important;
}

[MaxPSN]

Is there any way to get rid of the rounded corners? It was square on 150

Using urlbar_border_roundness.css with megabar_border_roundness in general_variables.css set to 0px only changed the search box

[MaxPSN]

Also would love to know if I can make those back to non-rounded corners too

[StevenSlater]

.urlbar-background { border-radius: 0px !important; }