[slightwinder]

No, it was not. That's a popular myth, but it's wrong. There were other browser with Tabs before opera event tried them. And Operas first attempts wasn't really Tabs in the modern sense. It was just a poor working button-bar for an MDI, which was a bit cumbersome to use. They fixed it two versions later, around the time when the feature gained attention in other browsers and even Mozilla Suit got it's first Extension that became so insanly popular that it was build into Phoenix (later renamend to Firebird, then Firefox) out of the box.

Though, Opera tried many things in that area. There never really lost the MDI-Spirit and went with different approached than most other TDI-Implementations. Made it more useful for some, more complicated for others. So for certain specific functions they probablly were the first ones.