Here is a minor bug that appears in Opera, but not in Internet Explorer:
When Opera checks for new messages, if there are replies for me I will hear the sound: "You have replies". So far, everything is normal.
Then, if I minimize Opera, I will hear the sound, "You have replies", again. If I bring it to the foreground again, I will hear the sound once again. Every time Opera loses or gets focus, the sound appears again - until I mark all messages as read or deleted.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)