What is the difference between “image/png” and “image/x-png”?

Question

What is the difference between \"image/png\" and \"image/x-png\"?

Answer 1

According to Wikipedia's article on Internet Media Types, and the article it cites...

Types or subtypes that begin with x- are nonstandard

So my guess is "image/x-png" is probably leftover from the days when png was pretty new, and as such, not standardized.