what is this whoof on safari?

I have a dozen or so places to click on my Safari tool bar, one of them being a2k, usually in first place, but hard to keep there because of all this other stuff -

Every other day or two, I obliterate a Safari tool bar tab by simply passing over it on the way to the back button, while, if I'd actually aimed at it earlier I'd have gotten miscellaneous detritis.

Am I index fingering wrongly? I've probably obliterated a2k forty times on my way to the Back button.

Is there some kind of trick to this?