I have been putting stylesheets on top (between <head></head>) of html. As far as I understand this is the best practice. (e.g. http://stevesouders.com/hpws/css-bottom.php)
Anyhow, recently I have experienced different results. Instead the codes below will return blank page when test.css is slow, which means I am not experiencing progressive rendering.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="test.css" />
</head>
<body>
Blah..
</body>
</html>
Then when putting test.css at bottom, I get progressive rendering.
<!DOCTYPE html>
<html>
<head>
</head>
<body>
Blah..
<link rel="stylesheet" href="test.css" />
</body>
</html>
As far as I have understood and tought so far, it should be the other way round.. Probably there are other factors that I have overlooked?
Google is fast busting the tradition of styles 'belonging' in the head. They do indeed recommend that critical styling belongs either in the <head> tag or even inline, but that other, non-essential styles should be referenced after the closing </html> tag. This does work on most, if not all modern browsers (I've not tested all).
The reason behind this is to load the bulk of the styles as a non-blocking reference, allowing the browser to begin writing to page before getting all the (potentially) bulky styles. Depending on what's in the 'critical' styles, this could cause an initial layout of hideous proportions before styling is rendered (FOUC). That is probably what you are experiencing with the "blank page" issue.
Remember also that CSS was released almost 20 years ago (1996), so it's not surprising that Google (and others) are manipulating and pushing out the traditional parameters of the concept.
A ridiculously simple example:
<!DOCTYPE html>
<html>
<head>
<title>It's a Brave New World</title>
<link rel="stylesheet" type="text/css" href="css/critical_styles.css" />
</head>
<body>
<!-- best page ever -->
</body>
</html>
<link rel="stylesheet" type="text/css" href="css/bulky_nonessential_styles.css" />