try Split Pannel Rated 3 out of 5 stars

Split Pannel can split firefox 4 with two panels ..
Only split two,....no more
if you just only want split the firefox 4 to two windows..
can try this add-on before Fox splitter is updated for ff4.
https://addons.mozilla.org/zh-TW/firefox/addon/split-pannel/
Good Luck!

This user has a previous review of this add-on.

Browser Splitting Was Useful Rated 4 out of 5 stars

I found quite a few uses for being able to split the view and see two things at once within the same window - it was a very useful functionality to have. Unfortunately, I have lost it because this doesn't work with Firefox 4.0. I really hope you or someone else will be able to come u pwith something that will work for 4.0, because I loved having this ability.

Special Thanks from Argentina Rated 5 out of 5 stars

Your proyect is awesome!! I've been using this addon for about a year to keep a requirement form allways on my browser. I'm waiting the FF4.0 update, hope you can make it!

Thank you so much!!

Rated 4 out of 5 stars

waiting for your support of ff4.0 ……

extensions.checkCompatibility.4.0 Rated 4 out of 5 stars

I thought, that I can still use the Fox Spiltter, if I deactivate the version-control of FF4.0 with about:config -> new Boolean -> extensions.checkCompatibility.4.0 -> false
But no new frame will open.... :-(

we want 4.0 Rated 5 out of 5 stars

i am waiting 4.0 version to update my firefox.

When will it support 4.0? any news?

Rated 5 out of 5 stars

Very cool extension. Hope FF4 support quickly.

hoping for ff4 update Rated 5 out of 5 stars

One of the most essential addons. i hope it gets updated to FF4. I'm currently using Tile Tabs instead, but it doesnt function quite the same.

Please, PLEASE update this for Firefox 4! Rated 5 out of 5 stars

Fox Splitter (Split Browser) is so good that without it Firefox is just another browser. I used it constantly, and miss its features terribly in Firefox 4. I have to completely change the way I work! Piro, will you please post here and let all of us know if you (or anyone) will be updating it? If so, I'll revert back to using it with Firefox 3, and try to wait patiently. Thank you.

Rated 5 out of 5 stars

Very Very useful and easy to use with a lot of ways to customize and good features as, context menus, buttons, button with drop-menu, firefox menu, focus on mouse, sync scroll, double click to expand and collapse (it is not in help), and fast way to split through costumized buttons in context area, two things i dont like much, it is context menu options at right click (back forward reload) as well as full expand pane works only in the main pane, and how open new tabs, but it gives good alternatives like toolbar buttons or dragging bookmarks to open a new tab in split pane. support F4 please!

Un module trop ancien / A module too old Rated 1 out of 5 stars

EN FRANCAIS / Le module n'a pas été mis à jour depuis 2009, n'est pas compatible avec Firefox 4.0 et semble abandonné. Un module équivalent et peut être même meilleur existe. Il s'agit de "Tile Tabs" qui est compatible avec Firefox 4.0 lui ! ............ IN ENGLISH / I would advice you to install instead of Split Browser another one "Tile Tabs" perhaps even the best and which works well with Firefox 4.0

This user has a previous review of this add-on.

Rated 5 out of 5 stars

guys please we need support for FF 4 latest beta !
please after working with this addon is hard to live without it

Rated 3 out of 5 stars

Hi,
This is a great add-on. However, is it possible to have a functionality in which browser can be split tab-wise. Currently, if a split a tab, the whole browser window gets split. Is it possible to selectively split certain tabs while not splitting other tabs?

Rated 3 out of 5 stars

The addon would be better if could actually do this:

http://img833.imageshack.us/img833/4386/dualview.jpg

screenshot explains all.

Rated 3 out of 5 stars

Causes issue with Firebug. The script window in firebug can become mis-aligned. Otherwise I like using it.

Rated 2 out of 5 stars

Seems to have broken the browser.tabs.closewindowwithlasttab = true config so that when the last tab is closed it doesn't close FF. Disabling this add-on puts things right again. Hence this add-on will be off my list until that is fixed.

Rated 5 out of 5 stars

STILL, no matter what you think, THIS AUTHOR DESERVES THE AWARD OF THE DECADE. Not until the likes of BroadPage 3.2.3 from 2000 to 2002 was there any such program. He either did a nice work-around the copyright or bought it. This program, as currently written, is still a fabulous program. - Mouse over right end of tab shows "close" for that tab. Menu options work fine for more functions. We are lucky to have this program available for FF and Wyzo browsers and not the "other" companies.

Rated 3 out of 5 stars

Good one.. Thanks

Bonne Idée MAIS .. Rated 2 out of 5 stars

L'idéal serait:
_ D'utiliser les boutons classiques du navigateur en fonction de la page ou l'on est, la page active, au lieu de créer cette barre dans le panneau qui en plus de ne pas être pratique, ne sert à rien.
_ De considérer le "panneau", comme un onglet ou une fenêtre apparentière pour qu'il soit compatible avec toutes les extensions, car pour le moment, et c'est le plus gros problème, le panneau est une sorte de page dans la page, et non une vraie page.
_ De pouvoir diviser une fenêtre de manière symétrique, ou du moins qu'on puisse le paramétrer pour que ce sois automatique, car la il faut recadre à chaque fois.

Je suis dans l'attente d'une grosse mise à jour, dans quel cas je désinstallerai, mais je salut malgré tout l'initiative.

Great but miss shortcut Rated 4 out of 5 stars

This addon is great, but there absolutly no shortcut.
For exemple: shortcut to reduce the tab or add/delete one.