ajax error handling logic

Question

In 2 ajax calls that are listed below, there are 2 places that say 'error: AjaxFailed'.

$.ajax({

type: "POST",

contentType: "application/json; charset=utf-8",

url: document.location.pathname + "/GetStudentLetter",

data: "{ " + strData + " }",

dataType: "json",

success: function (data) {

LoadEditor(JSON.parse(data.d), milestone);

},

error: AjaxFailed

});

if (milestone == '999') {

$.ajax({

type: "POST",

contentType: "application/json; charset=utf-8",

url: document.location.pathname + "/Gettattschyr",

data: "{ " + strData + " }",

dataType: "json",

success: function (data) {

successtest(eval(data));

},

error: AjaxFailed

});

}

}

function successtest(sletter) {

var sle = sletter

_txtattschyr = sletter.d

if (_txtattschyr > '1') {

alert('You have selected student(s) having more than one Entry for the current school year. ');

return

}

I would like to have better error handling so that I know what is exactly wrong. From the first ajax call, I got a 500 server error problem

in production. By guessing, I found out that I needed to increase the maximum size of the jason file that is posted above.

Thus can you tell and/or point me to urls that will show me better error logic that I can use?