Most likely these will be “errors of procedure,” or momentary personal squabbles that took place maybe four, six years ago.
Downvotes are also for (to varying degrees, depends on your pet peeves): spam nodes, errors of fact, blatant disregard for formatting, inappropriate (flame/troll), homework / job interview cheats, etc.
Errors of procedure, at least as I understand it, are cause for consideration not downvoting. There's not a whole lot of procedure around here, but posing in the wrong section comes to mind.
One thing that does bug me is when people post the same question repeatedly, and fail to notice all the replies they got the previous time(s). The urge to downvote such posts increases exponentially with additional repeats.