Agreed, popups are annoying. But Firefox doesn't seem to block them all properly, either. For example, try this [1] site. It's notorious for hijacking its own clicks; about 50% of the time you load that site, the search field will open a popup when you click on it to type. Same goes for real links. Unfortunately, I don't think there's a fix for Safari.

I don't know of a tree-style tab extension for Safari, sorry.

[1] http://rarbg.to/torrents.php