Complex sentence: A new feature targeted for Firefox 20 is a panel-based download manager, along with H.264 decoding on the tag, and per-window private browsing (per-tab private browsing on Android).
Split into simpler sentences: A new feature targeted for Firefox 20 is a panel-based download manager. Also planned for this version is H.264 decoding on the tag, and per-window private browsing (per-tab private browsing on Android).