Pressing TAB while browsing switches to/allows you to navigate links by keyboard.
Unfortunately, if you're halfway down a page and hit TAB accidentally, the page jumps up to the top link, losing your place. This happens to me a lot!
Since browsing the web by hitting TAB isn't very common (or easy), my suggestion is to have a prompt asking the user if they actually want to enter this "mode" when they hit TAB, just like the F7 (caret browsing) prompt:
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