What determines the example tags? (tags in the placeholder of the tags section when asking new question)

Question

When asking a new question on any site, you see a placeholder in the tags section. This contains three tags, like this example from the English Language and Usage site:

Or in words:

at least one tag such as (adjectives prepositions british-english) max 5 tags

How are the tags that appear in the placeholder determined?

Note: they do appear different at different times.

Answer 1

After some research, I believe I figured this out.

On each site, there is a job/task running every 12 hours or so (might be bit different, e.g. 10 hours) which will do the following:

• Pick three tags in random from the top 30 tags or so (again, might be bit different, e.g. top 25 tags or 35 tags), top meaning having most questions.
• Cache those tags server side, and use them as the "example tags" when asking new question.
• There is probably a check in place to prevent same tag from being used twice in a row.

The top tags are easily accessible in the tags page (e.g. on English Language and Usage).

To verify this, I have used the Internet Archive, taking https://superuser.com/questions/ask as example and finding a date with two snapshots:

1. March 11, 2016 06:22
2. March 11, 2016 22:59

As you can see, different set of three tags each time.