Mashq and Machine

While I was reviewing Opera Next’s changelog (11.50b1), I noticed this tidbit:

Start request for CSS resources now occurs during parsing.

What this means is that as soon as Opera encounters a <link> tag referencing an external stylesheet, it will issue an HTTP GET for that stylesheet. Most browsers parse the entire HTML source before requesting external assets. This also means that Opera will now start downloading the CSS before it starts rendering the page. Will that block rendering until the CSS is fully downloaded? It shouldn’t block rendering, but if it did, that would decrease FOUC (Flash of Unstyled Content) and FOUT (Flash of Unstyled Text) while slowing down rendering, of course. Let’s see:

Its interesting how Opera 11.50 does indeed download the CSS in parallel, but in this case its at the very end of the HTML download, even though the <link> tag is at the very head of the page. Perhaps some latency?

As for blocking rendering, its hard to tell. I have Modernizr and CSSUserAgent javascripts running, and javascripts in the head definitely block rendering until they execute, in most browsers, unless they are async’ed or loaded by something like LAB.js.

Overall, this is a welcome improvement. Although Opera has the smalled share of the desktop browser market, Hakon Lie and crew continue to deliver web-centric and developer-friendly features.