Mysterious blue circle below the icon of a pinned tab

[Odin2]

This small blue circle appears just below the icon of one of my pinned tabs. (The tab is for to-do.live.com.) If I activate the tab, the circle goes away, and then it stays away for an indeterminate time before it comes back. What is this circle? Can I remove it permanently?

[dickvl]

That blue dot on a pinned tab indicates that the page title has been modified (tab gets a titlechanged attribute) or otherwise the tab needs atention.
This can be used to alert you to check that tab.

See this section in the Firefox source code for what events can cause this dot to appear.
https://searchfox.org/mozilla-release/s ... nc.css#593

You can use code in userChrome.css with this selector and set the background property to none.

Code: Select all

.tabbrowser-tab:-moz-any([image], [pinned]) > .tab-stack > .tab-content[attention]:not([selected="true"]),
.tabbrowser-tab > .tab-stack > .tab-content[pinned][titlechanged]:not([selected="true"]) {
  background-image: none !important;
}

[Odin2]

Many thanks, dickvl. It seems that the blue circle can be useful [now that I know what it's for!], so I'll probably keep it.