user38807: I just got a few downvotes on different questions in a row without any explanation or suggestion. This kind of thing discourages new users and discourages people from learning about new things. Any mechanisms in place to make sure there is good justification?

user22057: It happens — I am often on the receiving end of this. You can tell when two completely different high-score answers are down-voted. Some pathetic individual has looked up your bio, seen the top answers, and downvoted them willy-nilly. As @Chris writes, if they overdo it the bot picks it up and reverses the downvotes.
Can’t do anything about it so better not to respond in any way, even (or especially) if you have a good idea who it is.
However, if you are a new user, make sure that you are following the guidelines. I have had responses to critical comments on several questions, suggesting I am targetting the individual, when in fact I hadn’t noticed it was the same person. The problem may have been that each question showed no prior research or was only answerable by opinion etc.

user5144: I looked into your profile and see only 4 downvotes in total, one from today, one from yesterday and two earlier ones. This is not what I would see as "mass downvotes". The biggest loss of reputation comes from the automatic deletion of a closed question.
Besides this, if mass downvotings happen (and this is characterized by a lot of downvotes in a short time) from the same user an automatic bot will detect this and reverse these votes automatically. This task is run once per day - if this does not happen and it's been well over 24 hours, please notify the mods.
The process of voting is anonymous (and is meant to be) so there is no way to know who downvoted you, not even the mods. It is not required to justify a downvote (or write an explaining comment).

38807: <p>I just got a few downvotes on different questions in a row without any explanation or suggestion. This kind of thing discourages new users and discourages people from learning about new things. Any mechanisms in place to make sure there is good justification?</p>
 22057: <p>It happens — I am often on the receiving end of this. You can tell when two completely different high-score answers are down-voted. Some pathetic individual has looked up your bio, seen the top answers, and downvoted them willy-nilly. As @Chris writes, if they overdo it the bot picks it up and reverses the downvotes.</p>
<p>Can’t do anything about it so better not to respond in any way, even (or especially) if you have a good idea who it is.</p>
<p>However, if you are a new user, make sure that you are following the guidelines. I have had responses to critical comments on several questions, suggesting I am targetting the individual, when in fact I hadn’t noticed it was the same person. The problem may have been that each question showed no prior research or was only answerable by opinion etc.</p>
 5144: <p>I looked into your profile and see only 4 downvotes in total, one from today, one from yesterday and two earlier ones. This is not what I would see as &quot;mass downvotes&quot;. The biggest loss of reputation comes from the automatic deletion of a closed question.</p>
<p>Besides this, if mass downvotings happen (and this is characterized by a lot of downvotes in a short time) from the same user an automatic bot will detect this and reverse these votes automatically. This task is run once per day - if this does not happen and it's been well over 24 hours, please notify the mods.</p>
<p>The process of voting is anonymous (and is meant to be) so there is no way to know who downvoted you, not even the mods. It is not required to justify a downvote (or write an explaining comment).</p>
