[webkit-dev] Question regarding priorities of subresource content retrieval

Silvio Ventres silvio.ventres at gmail.com
Tue Feb 8 02:23:41 PST 2011

This argument - "web developer is to blame for choosing a slow
ad/tracking/etc server" - is incorrect.
Web developers in general do not have any control over the ad provider
or, frankly, any other type of external functionality provider.
Google Analytics being a good point in case, you would not want most
of the world's web pages to suddenly hang if something happens inside

The web browser should clearly prioritize developer-controllable
resources over ones that are beyond web developer's control.
Also, as an application run by the user and not by the developer, the
browser should arguably prioritize actual content against
pseudo-content which purpose is functionality that is not visibile to
the actual user, such as ad/tracker scripts. This actual content has
higher probability to be important when sourced from the
domain/subdomain of the webpage itself, based on current trends.

Domain check is a reasonable approximation that fits both purposes.


On Tue, Feb 8, 2011 at 5:13 AM, Jerry Seeger <vikingjs at mac.com> wrote:
> I'm reasonably sure that javascript in the header must be loaded synchronously, as it might affect the rest of the load. This is why tools like YSlow advise Web designers to move javascript loads that are not needed for rendering until after the rest of the page loads.
> Blocking on loading the css is less clear-cut, as in some cases it could mean several seconds of ugly page. I don't know if it's right or wrong, but a lot of pages out there rely on the CSS being loaded before the page starts to render to avoid terrible layout and the appearance of items meant to be hidden for the seconds it takes the css to load.
> In general, while things could certainly be improved, it's up to the owner of the page to not rely on a a slow ad server, or build the page so the ads load after the primary content.
> Jerry Seeger
> On Feb 7, 2011, at 5:47 PM, Silvio Ventres wrote:
>> IE/Opera are delaying only for 4 seconds, same as Mobile Safari
>> The reason looks to be the url for the script/css.
>> If the url is the same twice, Chrome/Firefox serializes the requests,
>> while IE/Opera/MobileSafari launches both requests simultaneously.
>> Of course, requesting simultaneously doesn't fix anything, as you can
>> see by trying a link-stuffed version at
>> http://solid.eqoppa.com/testlag2.html
>> This one has 45 css and 38 javascript links. It hangs all browsers nicely.
>> The main point here is that it might be acceptable if it's coming from
>> the webpage domain itself.
>> But the links are coming from a completely different place.
>> This is exactly what makes browsing pages with any third-party
>> analytics, tracking or ad addons so slow and frustrating.
>> Fixing priorities in subresource download should make experience
>> considerably more interactive and fun.
>> --
>> silvio

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