Re: Media Queries and optimizing what data gets transferred

On Fri, Jan 25, 2013 at 10:01 AM, Andy Davies <dajdavies@gmail.com> wrote:
> My reading of the spec suggests that the UA could choose to defer the
> non-applicable stylesheets forever but there may be performance issues with
> that in some circumstances.

As Boris has explained, it's not performance issues, but rather author
expectations.  The average author expects a CSSOM to exist for all the
stylesheets in the page, and when the set of matched MQs changes, for
the styles to change at the same time, not a network-roundtrip later.
If any browser *did* defer them indefinitely by default, they'd get
compat bugs.

~TJ