One of the latest features of Opera version 9.5 is the ability to arrange tabs in cascade or in a grid. Open source developers were quick to come up with yet another extension to mimic the same effect in Firefox. The addon called Split Browser, allows you to split the viewing window of your browser so that you can view multiple tabs at the same time.
Split Browser is flexible and you can arrange the tabs in whatever way you like. To be honest, it's a little confusing and except the horizontally tiled, and the grid layout, any other layout pattern is essentially useless. The one and only use of this addon is if you want to compare multiple web pages, or want to keep a particular page on display at all times. Going by the download figures, however, it seems that it's quite a popular addon.
A lot of screen real estate is essential to do anything productive with this feature turned on.
A productive Split Browser layout
A not-so productive Split Browser layout