I also tested it on my iPhone and it didn't adjust to single column.
This code below works fine outside of Appery.io. But, if I look into Appery's generated code in the element inspector, I see that it creates a table, instead of nested divs, to make the grid. That may be why it doesn't work. No idea, just a thought.
Don
code
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>responsive-grid demo</title>
<link rel="stylesheet" href="http://code.jquery.com/mobile/1.3.1/jquery.mobile-1.3.1.min.css">
<script src="http://code.jquery.com/jquery-1.10.0.min.js"></script>
<script src="http://code.jquery.com/mobile/1.3.1/jquery.mobile-1.3.1.min.js"></script>
<style>
@media all and (max-width: 35em) {
.my-breakpoint .ui-block-a,
.my-breakpoint .ui-block-b,
.my-breakpoint .ui-block-c,
.my-breakpoint .ui-block-d,
.my-breakpoint .ui-block-e {
width: 100%;
float:none;
}
}
</style>
</head>
<body>
<div data-role="page" id="page1">
<div data-role="header">
<h1>Responsive Grid Example</h1>
</div>
<div data-role="content">
<div class="ui-grid-b my-breakpoint">
<div class="ui-block-a"><div class="ui-body ui-body-d">Block A</div></div>
<div class="ui-block-b"><div class="ui-body ui-body-d">Block B</div></div>
<div class="ui-block-c"><div class="ui-body ui-body-d">Block C</div></div>
</div>
</div>
</body>
</html>
/code