jQuery ajax error function

I have an ajax call passing data to a page which then returns a value.

I have retrieved the successful call from the page but i have coded it so that it raises an error in the asp. How do i retrieve that error from the jquery?

For example:

cache: false,
url: "addInterview_Code.asp",
type: "POST",
datatype: "text",
data: strData,
success: function (html) {
    alert('successful : ' + html);
    $("#result").html("Successful");
},
error: function (error) {
    **alert('error; ' + eval(error));**
}

It’s the error bit that I don’t understand. In the function what parameter do I need to put, so that I can then use the error message that I raised in the server.