On Sat, Jun 16, 2012 at 1:23 AM, Andy Davies <[email protected]> wrote: > I'm under the impression that a UA has to download all stylesheets > regardless of whether they will be used e.g. print, mediaquery may never > match etc. > > I've had a crawl through the specs but can't find the behaviour specified. > > Is my understanding right and if so can someone point me at the relevant > spec?
The relevant spec is just HTML, which pays no attention to the @media attribute when parsing <link rel=stylesheet>s. Without anything explicitly saying "Don't download X unless condition Y is met", you just download them all. The reasoning for this is that the set of stylesheets that you need for a document is not static - users *do* resize their browser, for example, and browsers would like to apply the relevant CSS immediately, not wait a second or so to kick off and finish a download. It also lets us keep the invariant that, if you use matchMedia or something to see if a MQ matches, all the styles are correct for the state of the world as you see it. ~TJ
