Back in 2011, Google launched Page Speed Service, an online service that automatically speeds up loading of your web pages. This was introduced after Google announced site speed as a ranking factor in its search results the year prior.
The company is now shutting down the service. It released a deprecation announcement, which says (via TechCrunch):
After 4.5 years of service, the PageSpeed Service team regretfully decided that the time had come to re-focus their efforts elsewhere and on 5th May announced that PageSpeed Service will be turned down. If you are using PageSpeed Service, you must change your DNS before 3rd August 2015 or your site(s) will become completely unavailable on that date.
Explicit notification will soon be sent to users that we believe are affected, however you should not rely on this! We recommend that you login to the console and look at your list of domains. Anything that shows up as "Enabled" is at risk.
The console will give users advice if they try to delete a domain that is live. You'll have to do it by August 3rd or your site will break. There are detailed instructions here.
Google does offer the same PageSpeed technology in other services, and provides a list of alternatives that aren't affected by the deprecation. As it notes, may web hosting providers already integrate PageSpeed, and there are PageSpeed modules for many common web servers.
Image via Google