AJAX jQuery Success but no change

Okay so I got this txt file that I'm reading from the wamp local server,

I make changes to this text and try to send it back to the file

the ajax request fires the success function but the file doesn't change, any ideas? thanks

Code:

var customCss = "";
var customCssPath = "http://localhost:8081/userThemer/styles/custom.css";
var newStyle ="newwww";
    $.ajax({
        type: 'POST',
        url: customCssPath,//url of receiver file on server
        data: newStyle, //your data
        success: function () {
            console.log("YAY !");
        },
        error: function () {
            console.log(":'(");
        },
        dataType: "text" //text/json...
    });