'breadcrumbs' are a trail. there's a list across the top which shows where you've been ie forums>Life>speakers corner it shows where you've come from so you can go back there again. ad_above_top_breadcrumb is probably a 'placeholder' where an ad should appear if you're not a subscriber, or not logged in, but, for some reason didn't appear, perhaps the link to the ad was broken, hence the placeholder name appeared. Just my thoughts. As you said, it's gone now, because you reloaded the screen and it fixed itself.
Ahh just some old red shite, all binned. Should have taken a photo really, ducbird would have loved it.
No just accumulated stuff from over the years, non of it of any real value but it's time to get ruthless.