I imagine this has been asked time and time again, but i've not seen the answer I'm looking for.
Im doing some simple tests with a HTML file and CSS file trying to stop the page from render blocking the CSS, running the site through page insights ( google )
Now i've seen answers like this:
<link rel="stylesheet" href="style.20180530.css?ver=1.0" media="none" onload="if(media!='all')media='all'">
and I've seen answers like this:
<link href="https://fonts.googleapis.com/css?family=Roboto:300,700" rel="preload" onload="this.rel='stylesheet';this.removeAttribute('onload');" as="style">
Both of which I am fine with, for the google fonts! But not for the main styles of the page, I don't think its a good user experience to see a page with no styles and then all of a sudden they load in.
Obviously you can eliminate any blocking of CSS by sticking the whole lot as inline styles, but again I don't think this is good practice, you're outputting all styles to a HTML page and not loading them via a style sheet.
I've seen sites actually load the styles like so:
<link rel='stylesheet' id='main-css' href='./style.2018052108.css?ver=4.9' type='text/css' media='all' />
Heres a link to the page insight speed test on the. I know the site is running wordpress. If you view page source it uses the exact same as i've used above.
And they aren't Render Blocking at all... How?
Im on a https I'm using cloudflare and my style sheet is compressed and only around 24bytes and I'm still getting render blocking.
The CSS loaded as an external request is always render blocking, you can't avoid it. The recommendation on pagespeed insights is that you don't do any css request before the content is loaded, in order to avoid the unstyled effect they suggest that you inline the CSS needed to display the content before the fold.
The page on your example is doing exactly that, they inline some css content (check the source code and search for the style tag), then, when the content is loaded they add an external stylesheet with javascript.
All that said, this is a recommendation, you can ignore it if you are happy with the performance of your page, if you want to follow the recommendation you can apply some techniques to achieve this in an automation way.
As always, in css-tricks you have a great introduction post to these techniques: https://css-tricks.com/authoring-critical-fold-css/