In Firefox Mobile for Android, when viewing the open tabs as thumbnails, there is a tiny square image (similar to a favicon) to the left of each webpage title.
I'm pretty sure it's not a
favicon because a large number of websites don't display an image. Whenever the image is missing, Firefox Android simply uses a white capital letter in a coloured square, instead.
However, I'm struggling to find out what it is.
What is it? What
<meta> element does Firefox Mobile source it from?