Flash Lite 3.x did not support AS3 (introduced in Flash Player 9), meaning content specifically built for newer desktop players would not run.
Support for ActionScript 2 (AS2), local connections, CSS, and HTML text. 🛠️ Limitations & Technical Constraints Adobe Flash Lite For Nokia 5800
Full support for FLV (Flash Video), the primary format for sites like YouTube and CNN at the time. Flash Lite 3
Although version 3.1 improved memory management for images, the 5800's limited 128MB RAM often led to browser crashes on heavy Flash-based websites. Adobe Flash Lite For Nokia 5800
Adobe claimed compatibility with 91% of the top 500 internet sites.