HELP! I can't any longer just go BACK one screen while in email or when on the Internet?Have to use control {.

My husband and I just noticed a week or so ago that we had lost the (now intuitive) arrow(or what exactly it was, we can't even remember because it had become so intuitive/natural all the time... to "go back" when we are on our computer. Instead, we now have to use something like "control { (left bracket) " and I have no idea how my husband even figured that out! This is when I'm using Safari and/or checking email with Yahoo, or both or one. It's all the time now, no "arrow" to help us as an option anymore. Any ideas of what's up? Thanks so much!