Google's Recommended Guidelines for Optimizing Mobile Websites

3 Points to Keep in mind while building your website for smart phones.

1) Sites that use responsive web design, i.e. sites that serve all devices on the same set of URLs, with each URL serving the same HTML to all devices and using just CSS to change how the page is rendered on the device. This is Google’s recommended configuration.

2) Sites that dynamically serve all devices on the same set of URLs, but each URL serves different HTML (and CSS) depending on whether the user agent is a desktop or a mobile device.

3) Sites that have a separate mobile and desktop sites.