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And of course, you need some extensions to go with your FireFox. There are so many great ones: ForcastFox, Google Toolbar, TabFX, Web Developer. To install some of these old standards, go to Tools>Extensions and click to link at the bottom of the extensions window to "Find new extensions."
A new version of Firefox often leads to some issues with extension compatability. (E:Paul)'s fave, Live Headers is no longer available, but I'm sure it will be soon.
And with a major upgrade like 1.5, new plugins are available.
First up: Foxpose
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Fans of the Mac OSX Expose feature will know what to expect here. Foxpoxe puts a button in your status bar that wil display all of your open tabs in a visual grid.
And Also Hotness: Tab Preview
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This extension makes it so that thumbnail previews of each page pop up when you hover the mouse over the tabs. It's a super fast way to scan through a set of open tabs. Tab browsing addicts will love it.
Happy browsing, Buffalo!
Most of the other email providers (including Yahoo) have had this feature for a long time.