Or sometimes you want to be able to load two pages side by side, and not in the multiple windows sense. I use both Spurl and MetaWishList, both of which can use a 'sidebar' feature in Firefox to open a second web page in a small bar to the left of the current page. Particularly in the world of "Web 2.0" (I don't really like the term...) there is a need for the ability to quickly load little 'pagelets' without leaving the current page.