Custom css
Use custom css for better user experience
Survey.Survey.cssType = "bootstrap";
Survey.defaultBootstrapCss.navigationButton = "btn btn-green";
var myCss = {
    matrix: {root: "table table-striped"},
    navigationButton: "button btn-lg"   
};
var json = {questions: [
{ type: "matrix", name: "Quality", title: "Please indicate if you agree or disagree with the following statements",
   columns: [{ value: 1, text: "Strongly Disagree" }, 
              { value: 2, text: "Disagree" }, 
              { value: 3, text: "Neutral" }, 
              { value: 4, text: "Agree" }, 
              { value: 5, text: "Strongly Agree" }],
    rows: [{ value: "affordable", text: "Product is affordable" }, 
           { value: "does what it claims", text: "Product does what it claims" },
           { value: "better then others", text: "Product is better than other products on the market" }, 
           { value: "easy to use", text: "Product is easy to use" }]}
]};

window.survey = new Survey.Model(json);


survey.onComplete.add(function(result) {
    document.querySelector('#surveyResult').innerHTML = "result: " + JSON.stringify(result.data);
});


$("#surveyElement").Survey({ 
    model: survey ,css: myCss

});

<!DOCTYPE html>
<html>
<head>
    <title>Use custom css for better user experience for plaform jQuery, SurveyJS Library Example</title>
    <script src="https://unpkg.com/jquery"></script>
    <script src="https://surveyjs.azureedge.net/0.96.3/survey.jquery.js"></script>
  
    <link rel="stylesheet" href="https://unpkg.com/bootstrap@3.3.7/dist/css/bootstrap.min.css">
    <link rel="stylesheet" href="./index.css">

</head>
<body>
                <div id="surveyElement">
            </div>
    <div id="surveyResult"></div>

<script type="text/javascript" src="./index.js"></script>

</body>
</html>
.btn-green {
  background-color: #1ab394;
  color: #fff;
  border-radius: 3px;
}
.btn-green:hover, .btn-green:focus {
    background-color: #18a689;
    color: #fff;
}
.panel-footer {
    padding: 0 15px;
    border:none;
    text-align: right;
    background-color: #fff;
}

Set the css property to override the required css class(s).

Currently you may override the following css classes: