JQuery Ajax Post results in 500 Internal Server Error

I suspect that the server method is throwing an exception after it passes your breakpoint. Use Firefox/Firebug or the IE8 developer tools to look at the actual response you are getting from the server. If there has been an exception you'll get the YSOD html, which should help you figure out where to look.

One more thing -- your data property should be {} not "{}", the former is an empty object while the latter is a string that is invalid as a query parameter. Better yet, just leave it out if you aren't passing any data.

in case if someone using the codeigniter framework, the problem may be caused by the csrf protection config enabled.

This is Ajax Request Simple Code To Fetch Data Through Ajax Request

$.ajax({
    type: "POST",
    url: "InlineNotes/Note.ashx",
    data: '{"id":"' + noteid+'"}',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(data) {
        alert(data.d);
    },
    error: function(data){
        alert("fail");
    }
});

I just had this problem myself, even though i couldn't find the reason for it in my case, when changing from POST to GET, the problem 500 error disappeared!

 type:'POST'