AMP - Accelerated Mobile Pages

https://www.ampproject.org/docs/

 AMP Boilerplate Code

AMP HTML documents must contain the following boilerplate in their head tag. Validation is currently done with regular expressions, so it's important to keep mutations as minimal as possible. Currently, allowed mutations are: (1) inserting arbitrary whitespace immediately after the style tag opens, and immediately before it closes; (2) replacing any space in the snippet below with arbitrary whitespace.