Ah, the great features Opera had for ages until they dropped everything. Safari adds them and it's all big news. Read a tech magazine recently that was so excited about this "amazing and ground-breaking new feature" that I wondered if they had ever used Opera before.
With that being said, yeah, being able to apply custom stylesheets to websites easily is great!
With that being said, yeah, being able to apply custom stylesheets to websites easily is great!