It’s a mobile world.
The next 4B users are going to use the web only on mobile so we should think on their experience. Moreover, a lot of people are using the mobile web as discovery mechanism and when they land on our site we got the (one) chance to impress. The summary of the slides below will focus on two main aspects: performance and user experience. In the slides you can read on the 25 principles and how to work with them.

• Performance
  Get content to the user as quickly.
  I think this formula used in Ilya Grigorik’s talk sums this up:

  Perceived performance = f(Expected Performance, 
                             UX, 
                             Actual Performance)

• User Experience
  Optimize for the mobile device. So start your design from the small screen and move forward to a bigger one.

Here are tools that every web developer should use (or embrace the concepts that these tools promotes):

• Development: Web Fundamentals and Web Starter Kit to get all the principles out of the box.

• Testing and improvements: PageSpeed Insights and Web Page Test