Why no icon displayed?

Why no icon displayed?

Why does the following code not display an icon?

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href=" https://code.jquery.com/mobile/1.4.5/jquery.mobile.structure-1.4.5.min.css">
<script src=" https://code.jquery.com/jquery-1.11.3.min.js"></script>
<script src=" https://code.jquery.com/mobile/1.4.5/jquery.mobile-1.4.5.min.js"></script>
</head>
<body>
<div data-role="page">
<div data-role="content">
<a href="xxx.html" class="ui-btn ui-input-btn">Delete</a>
</div>
</div>
</body>
</html>