Nokia Series 40 - Platform

Series 40 is the world's most widely used mobile platform: Hundreds of millions of Series 40 phones are in use every day.

Series 40 supports two app development environments. Java ME gives you the ability to create apps that require high performance, such as games; and Series 40 web apps, which are enabled through the Nokia Browser for Series 40, to offer straightforward delivery of web-centric applications with a rich user experience. Series 40 phones range from entry level products that provide many mobile consumers with their first Internet experience to high-performance, full-featured phones such as the Nokia Asha 311.

Currently, you can target over 150 phone models with Series 40 apps.

Source : Nokia Developer