From the ‘Nightly Open Source Innovation’ files:
Firefox 20 is sure shaping up to be a really big release for Mozilla. We already knew that it would finally be the release that provides Private Browsing as it should be. Now it looks like Firefox is finally getting a really interesting Network load fix that seems obvious and sure could make a huge performance difference.
Firefox 20 will load stylesheets before images.
Yup I know. Seems so ridiculously obvious doesn’t it?
The bug is titled,” Make sure that we load stylesheets and scripts with a higher priority than images.”
Mozilla developer Ehsan Akhagi wrote:
“I don’t know what our heuristics in the load priorities look like, but it seems to me that images (at least those which won’t affect layout) should have a lower priority compared to stylesheets and scripts in order for us to be able to get something to the screen faster.”
Akhagai is of course correct and a patch is now in place. Preliminary testing done by Mozilla developer Patrick McManus shows some promising results as well. Using the popular social networking site pinterest as an example, the wait time to get something to show up the screen, dropped from 3.4 seconds to 1.6 seconds.
I suspect that users will notice an observable difference as a result of this change across a wide variety of site.