Why this guide?
Every major open-source project has its own style guide: a set of conventions (sometimes arbitrary) about how to write code for that project. It is much easier to understand a large codebase when all the code in it is in a consistent style.
“Style” covers a lot of ground, from “use camelCase for variable names” to “never use global variables” to “never use exceptions.” This project holds the style guidelines we use for Google code. If you are modifying a project that originated at Google, you may be pointed to this page to see the style guides that apply to that project.
-- from google-styleguide project home
These style guides are licensed under the CC-By 3.0 License, which encourages you to share these documents. See http://creativecommons.org/licenses/by/3.0/ for more details.