Much more speed with later loading images

In many cases pages contains images there are only visible if someone scroll the page.
That is the simple trick i used here - these images are only loading if there coming in the visible area.
See the results of the simple testpage:

Original page is here:

In the results only 3 images are loading - 3 from 43 with a size of 720 x 326 px and total of 2,1 mb.

Pagespeed 100/100.

In the real world of internetshops with 80 … 120 small or middle sized images on a page the pagespeed jumps immediately to a very high score.

David Artz has a library that helps automate it:

It isn’t limited to images and lets you set buffer zones so it starts to load it when you get close. Not sure if he added it yet but I wanted to also force trigger the load off of a timer attached to onLoad.

Nice results score. You should also set good expiry limit for images.