Almost 6 years ago, I wrote a blogpost A new website for the Stacks project announcing the first version of the Stacks project website. Today v2 has been released, see stacks.math.columbia.edu.
I would like to thank Raymond Cheng and Johan de Jong for the hard work we've done together, and Peter Woit for helping us with the server administration.
The main point of the new website as a user is that it is mobile-friendly. It should look good on tablets and smartphones, and if it doesn't, please tell us.
Less important for your average user, but very important to us, is that the system (called Gerby), is much more flexible. See the website for Gerby for more information.