title: What can trigger an Ajax 404 error on url that exists... and works?
body: <p>I make an ajax call on an url that does exists, and does work, even when called with ajax.</p>
  
  <p>Checking with firebug, the POST request fail due to a 404 error, but if I expand the data about the post request, in the response tab, I do find correctly the data that it is supposed to return.</p>
  
  <p>So, everything <em>is</em> working (this is an login system, and users gets <em>logged</em> in), but the page still results as 404 error.</p>
  
  <p>I don't have any clue about what can be causing this. I'm not sure either what code should I post, since this looks to me very strange and unexplainable. 
  By the way, the same code seems to work on other pages. Anyone has some idea of what could possibly causing this kind of behaviour?</p>