CSS doesn't block rendering on Firefox Quantum : <p>With Firefox Quantum I noticed a "glitch" on loading the CSS of some websites.</p>

<p><strong>One of these is <a href="https://www.doveconviene.it/discount" rel="noreferrer">my company's website</a>:</strong></p>

<p><a href="https://i.stack.imgur.com/OyNr1.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/OyNr1.gif" alt="DoveConviene Website"></a></p>

<p><strong>Or Github too:</strong></p>

<p><a href="https://i.stack.imgur.com/VrRYC.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/VrRYC.gif" alt="Github Website"></a></p>

<p>In the first one, we have only one CSS file in the <code>&lt;head&gt;</code> section of our pages.</p>

<p>It seems that - only in Firefox Quantum - the CSS doesn't block the render of the page <a href="https://developers.google.com/web/fundamentals/performance/critical-rendering-path/render-blocking-css" rel="noreferrer">as it should</a>. The rest of the page loads without the CSS for some instants, then the CSS is applied as if it loads asynchronously (but it's not).</p>

<p>Obviously, this behavior doesn't happen in all the websites I visited.</p>

<p>I really have no clue what's going on :)</p>
