A long, long time ago, just before the end of the browser wars, Netscape made a last ditch effort to remain relevant. It decided to skip version 5, and rewrite their browser from the ground up. When they showed off the preview release of version 6 (PR 1), reactions were not favorable.
However, the default theme it shipped with had promise, and although it was abandoned quickly, it's been recreated for Vivaldi, with matching icons. For those of us who remember.