Thanks, Joe. I closed Firefox and opened IE. (I'm still on it) Sure enough, I was able to delete all the Gmail emails. I don't understand WHY?

In the meantime, thanks for all your suggestions, everybody. I'm tracing this thread for future reference.

Jeri, Super Adblock Plus is a popup control. I think it works very well- at least, I haven't seen any since I installed it. It offered a free trial period before one has to purchase it- for the last couple of days it says that my free trial has expired, although the logo has not disappeared. Think I'll wait and see if ads start popping up. If they do, it means that it has been disabled and it may well be worth purchasing. Otherwise, maybe I'm just not getting ads. (?)