Admin Forum:What creates the speech bubble "tail"?

You know that little triangular "tail" on speech bubbles that points back to one's avatar? It can be seen easily enough on the User Profile Masthead or on the first post of a thread with the new forums/Message Wall/Blog. What is creating that? I've been trying to select it with the Firefox console mouseover, but I can't specifically choose it. Is it some image that's z-indexed down below the level of the main div that's floating on top? 00:09: Mon 03 Dec 2012


 * Those little triangles are created using the :before and :after pseudo-selectors, which is why you can't click on them. To find them, you actually have to inspect elements near them until you (hopefully) find the one on which the pseudo-selector was used.


 * Here's sample code demonstrating what selectors to use.