1. Reference to places in Colorado due to the first 3 digits in a phone number, also known as an area code. the area code is in places such as Denver and Highlands Ranch. A very boring place to live, inhabited by rich, carefree white people, and stoners.
2. A white rap group in Highlands Ranch who arent that great.
Rich white kid: "I live in the 303!"
Other guy: "Youre happy about that?"
Rich white kid: "Hell no"