What is 1e100.net?
1e100.net is a Google-owned domain name used to identify the servers in our network.
Following standard industry practice, we make sure each IP address has a corresponding hostname. In October 2009, we started using a single domain name to identify our servers across all Google products, rather than use different product domains such as youtube.com, blogger.com, and google.com. We did this for two reasons: first, to keep things simpler, and second, to proactively improve security by protecting against potential threats such as cross-site scripting attacks.
Most typical Internet users will never see 1e100.net, but we picked a Googley name for it just in case (1e100 is scientific notation for 1 googol).