Stop Hotmail/Outlook.live from Asking to "Add Application"

Noticed recently that the tab in Firefox with Hotmail open started displaying an 'add "outlook.live.com" as an application for mailto links?', which is annoying since it keeps coming back on every refresh.

One way to get rid of this (hat-tip to /u/xeq937 via this thread):

• Open about.config
• Set network.protocol-handler.external.mailto to false.
• Refresh the hotmail/outlook tab

Haven't noticed any downsides to doing this as yet.

Settings for Tree Style Tab in Firefox 57

Firefox 57 changed the plugin API extensively, and all plugins underwent major changes. One of which was Tree Style Tab, which lets you (among other things) display tabs down the side of the page rather than across the top.

In Firefox 57, the default look with Tree Style Tab had a number of issues for me, namely:

• The regular tabs (across the top) were still visible, even when the tree tab was visible
• The box to close Tree Style Tab was disproportionately large, and I never turn it off anyway
• Each tab in the list was much thicker vertically than previously

Scouring around the internet I came up with the following changes to fix all of the above:

• Add the following to userChrome.css (sourced from this post at /r/Firefox). Create in ~/.mozilla/firefox/<custom>.default/chrome if needed:

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

/* to hide the native tabs */
#TabsToolbar {
  visibility: collapse;
}

/* to hide the sidebar header */
#sidebar-header {
  visibility: collapse;
}

• Add the following to the "Advanced" section of the Tree Style Tab preferences from within Firefox, which mostly came from the posts at this Hacker News thread:

.closebox {
  display: none;
}

.tab:hover .closebox {
  display: block;
}

:root {
  --tab-height: 24px;
}

.tab {
  height: var(--tab-height) !important;
}

#tabbar .after-tabs {
  display: none !important;
}

• In "Hamburger" menu -> Customize, in the bottom left check "Title Bar" if you want it visible

Update 7 Apr 2020: I noticed in new installs that the visibility options weren't being applied properly. As per this comment from MikeF, you now need to go into about:settings and change toolkit.legacyUserProfileCustomizations.stylesheets to true and restart the browser. Thanks Mike!

Fix KDE Unreadable Tooltip Text/Background Colours in Firefox

In a recent update to Firefox (v46), when running under KDE on Kubuntu 14.04, the choice of text colour when hovering over images or other items in the browser that pop up a tooltip was essentially unreadable. Here's an example:

This is due to Firefox (for whatever reason) using the "WindowText" system colour rather than the "TooltipText" colour.

There are a couple of ways to fix it. The first is to go into the "Colors — KDE Control Module" and select a new colour scheme that has a better contrast in those two colours. Out of the defaults in KDE, I found Honeycomb, Norway, Obsidian Coast, Oxygen Cold and Zion all looked okay.

The other way is to override the tooltip colours.

On the same dialog, click the "Colors" tab, and find the Tooltip Background colour. If it's a dark colour, change it to something light, or light if it starts dark. You might also want to change the Tooltip Text colour to complement it.

Another option is to change the Window Text colour, but this colour is used in many more places, so will affect the look of all other applications.

This thread on the Arch Linux forum has a lengthy discussion on the issue.

Addendum: for Tree Style Tab users, changing the colour settings doesn't help. The selected tab highlights itself using the Window Text colour, the same colour as the text. To get around that one I changed to the Oxygen theme, rather than the default theme. That fixes most things up, but some sites override the colour of the text in dropdown boxes, but don't override the background...so it becomes close to unreadable. Annoying.