Why does a 415 error appear when submitting via $.post?

Question

JavaScript

Hello! Not so long ago, for no reason, an error began to appear: 415 Unsupported Media Type
if a request to the server is sent like this:

$.post('/ajax/load', {act: act}, function(d){
   //....
});

But you just need to change $.post to $.get - everything is fine. Data on the server is received via $_REQUEST. Previously, everything worked perfectly, nothing was done with the code.
Tell me where to dig?

Answer 1

https://developer.mozilla.org/ru/docs/Web/HTTP/Sta...
https://stackoverflow.com/questions/19396696/415-u...