Learning Objective - Content

I get that.
What I'm curious about is the choice of prefetching the images to the browser cache, over the standard just in time image fetching. (its a new shiny web feature, that has [specific use cases that it works well in](https://developers.google.com/chrome/whitepapers/prerender))
also I haven't seen an ```id``` used in the ```<head>``` section of html before, is there functionality linked to the ```id```?