I’ve just noticed that I’m no longer getting the little yellow and blue “SD” icon in my address bar. It still shows up for the Straight Dope home page when I check out Cecil’s latest.
What happened?
I’m looking at it right now. So it’s not a boardwide thing.
I see it as I’m typing this. Maybe it’s controlled by a browser setting?
This happens occasionally. Clear your internet cache and the favicon (that’s the name for these things) will be recreated next time you visit SDMB. (Enter ‘missing favicons’ into Goog;e for if you need more info.)
Aldiboronti gave excellent advice. On occasion, however, a browser or the operating system will crash, or something will terminate unexpecedly, or the whole system will just lock up. When that happens, you may accumulate what’s called “orphaned files” — temporary files that were not deleted, even when you clear your cache. (Incidentally, uninstalled programs often leave behind orphaned files as well.)
They also leave behind orphaned entries in your Windows registry.
The best tool I’ve seen for this problem is CCleaner. It’s free. It works great. You can even encrypt your deleted files to remarkable depths, so that even the CIA would have great difficulty recovering them if they could at all. I use the software practically every day, and I use it to clear my Internet cache precisely because it gets those orphaned files and folders that the browser misses.
They’re back! I didn’t do nuthin’ and they’re back.
Welcome back, little favicons!
Leave them alone and they will come home,
Bringing their tails behind them. 
You can do a deep refresh of a current web page with the key combination <CTRL>-<F5>.