The Verizon / AOL deal has brought up an interesting data point: AOL still has 2.1 million dial customers ( page 4 in the PDF ).
Combined this with the number of Internet users in the United States ( ~279 million ) you get: ~1% of United States Internet users are on AOL dial up.
I ran www.google.com through WebPageTest, comparing Cable ( 5 Mbps down, 1Mbps up, 28ms RTT ) to 56k dialup ( 49Kbps down, 30Kbps up, 120ms RTT ). The result:
And google.com is fast compared to most sites, nearly every modern web site is going to be horribly painful on a dialup connection.
You may remember one of the original webperf rules was to put scripts at the bottom.
Patrick Meenan on how it is supposed to work ( emphasis mine ):
– The preload scanner scans the whole document as it comes in and issues fetch requests.
– The main parser sends a signal when it reaches the start of the body and sends fetch requests for any resources it discoveres that are not already queued.
– The layout engine increases the priority of in-viewport visibile images when it does layout.
– The resource loader treats all script and css as critical, regardless of where it is discovered (in the head or at the end of the body). see crbug.com/317785
– Resource loader loads in 2 phases. The first (critical phase) delays non-critical resources except for 1 image at a time. Once the main parser reaches the body tag it removes the constraint and fetches everything.
TL;DR: don’t use defer for external scripts that can depend on eachother if you need IE <= 9 support
Even after 20 years of development there are days where browser environments still feel like the wild west.
Patrick Meenan mentioned first paint time improvements in Chrome 41. I noticed a ~25% improvement in the first view SpeedIndex times for one of our tests. It was easy to spot when the auto update from Chrome 40 to 41 happened:
I compared the individual tests before and after the update and this really is all about first paint times. The total time for the page to be visually complete was roughly the same.