It's always easy to tell apart the people who know shortcuts from the people who don't, if you watch them use their computers. Someone with a few shortcuts on tap will zoom around their monitors, switching between mouse and keyboard only when necessary.
But there are a few shortcuts and user interface quirks that are too outdated and weird, and only serve to surprise and annoy us. They herald from an earlier age when people were still figuring things out in new UI paradigms. For example, these days, you expect the scroll wheel to scroll up and down in a scrolling view. However, my coworker was changing some project settings in Visual Studio the other day, and he tried to scroll through the settings while a drop-down menu in the settings had focus. It scrolled through the menu options, selecting them, instead of scrolling through the view. He had to cancel the changes he was making and open the window again, because he couldn't remember what was originally selected.
This is the worst kind of surprise. Something you thought was just supposed to let you look at different parts of the interface instead modified the data you were looking at. Backspace to go back is a similar surprise. It's supposed to delete text, but instead it can navigate away from a page entirely, if you are in the wrong state when you press backspace. For the same reason, I'm even getting sick of the old middle mouse button paste, since it's too easy to press when I'm scrolling.
Forward and back navigation are already mapped to alt + left and right arrow. Let's reserve backspace for deleting text. (I'm not happy that it sometimes means "navigate up a level", but that might tell you what kind of computer I had growing up.)