Since you are using a resource file for the popup's content, it's best to load the remote script from the crossriderMain function, as follows:
<!DOCTYPE html>
<html>
<head>
<!-- This meta tag is relevant only for IE -->
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<script type="text/javascript">
function crossriderMain($) {
appAPI.db.async.get('style-css', function(rules) {
$('<style type="text/css">').text(rules).appendTo('head');
});
appAPI.request.get({
url: 'http://www.google.com/jsapi',
onSuccess: function(code) {
$.globalEval(code);
appAPI.db.async.get('script-js', function(code) {
// runs in the context of the extension
$.globalEval(code.replace('CONTEXT','EXTN'));
// Alternatively, run in context of page DOM
$('<script type="text/javascript">').html(code.replace('CONTEXT','PAGE DOM')).appendTo('head');
});
}
});
}
</script>
</head>
<body>
<h1>Hello World</h1>
<div id="feed"></div>
</body>
</html>
[Disclaimer: I am a Crossrider employee]