I have seen three different ones, and two of them I really don't understand how to interpret well.
- Just a key. That's what I usually see, and its meaning is obvious
- A key with what looks like off-kilter parentheses or perhaps circular arrows. What's that mean? That usually goes away after a couple of minutes.
- A key with a faint red circle overlaid. Obviously it's a caution symbol. This tends to appear when a browser is first opened and stays until the first time I click on the key icon. What's this?