... Chrome and Opera already have this.

Here's Firefox's explanation:
http://blog.mozilla.com/faaborg/2010/06/24/why-tabs-are-on-top-in-firefox-4/

And I'm still using my operating system tabs, not the browser tabs, for tabbing across pages... one benefit being it works across all apps, not just browsers... hope future browsers will let me opt out of their own tabs easily.

Philipp: but your future browser will only support Web apps!
Did you know you can add the flag --enable-vertical-tabs in Chrome Dev and Chromium
http://lh5.googleusercontent.com/_8ghhA1BQqIM/TA-THcnzzYI/AAAAAAAAKiM/uapujiwmHRs/s1024/sideTabs.jpg (via http://www.google.com/buzz/beaufort.francois/iZcsrhUoybQ/With-the-upcoming-of-Google-Chrome-OS-tablets-side).

Philipp wrote:
> ... I'm still using my operating system tabs ... hope future
> browsers will let me opt out of their own tabs easily

You need to also hope that future operating systems won't be unified with their browsers.

I'd like to see some integration between tabs and OS apps. Or at least a friendly full screen mode!
It's a matter of time, isn't it?

An interesting question is: why did browsers add their own tabs, and why do most users prefer the browser tabs to the operating system tabs?

I think the answer is that the browser tabs freed the users from doing a log of window jugging: rearranging windows to the size and position they want them. If you use browser tabs, you just size and position your browser windows once (I use two 960pixel-wide browser windows side-by-side) then let the browser manage the individual website tabs after that.

But browser tabs came in when most websites were still table-based, and much better at adapting to whatever browser width you were using. The switch to CSS, although good in most other ways, brought reduced flexibility to lay out a website fluidly, and today many websites have a specific pixel-width at which they display best.

For that reason, a reunification of browser tabs and OS tabs might be a good thing. But I think the innovation will be coming on the browser side (with application tabs) rather than on the OS side.

> The switch to CSS, although good in most other ways,
> brought reduced flexibility to lay out a website fluidly,
> and today many websites have a specific pixel-width
> at which they display best.

I'm not sure this is necessarily the reason why more websites use fixed-width designs. Although trickier for the inexperienced, you can still create fluid designs using CSS and DIV elements rather than a TABLE-based design.

I'd guess that the increase in fixed-width designs is more to do with site visitors using much larger resolutions and designers wanting to keep their pages looking pretty and more readable in larger browser windows. (Of course, a more elegant solution is to use a max-width instead so that users on smaller resolutions don't have to scroll horizontally...)

> elegant solution is to use a max-width

Browser support for "min-width" and "max-width" has only recently reached critical mass. I hope we'll see it much more widely used in the future.

> I think the answer is that the browser tabs freed the
> users from doing a log of window jugging: rearranging
> windows to the size and position they want them.

Hmm, I usually have all windows maximized. Be it a text editor, a photo editor, a browser etc. (A decade or so ago it was usually needed to resize the browser so that you don't have long line lengths, but that's no issue anymore for the majority of sites.)

Took me some special gadgets to recreate this – tab-switching and maximized windows – on a Mac, but now it works there too :)

> You need to also hope that future operating systems
> won't be unified with their browsers.

If that's the case, then all I'd need is a left-hand, auto-collapsing tab bar provided by the browser. For some reason I don't like clutter on my screen, and information about which other unused apps are open at the moment is kind of a distraction and wastes a bit of screen space. But that may be just personal taste.

>> An interesting question is: why did browsers add their
>> own tabs, and why do most users prefer the browser tabs
>> to the operating system tabs?

What do you mean by "operating system tabs"? Note that tabs are different than windows and tiles. I think there may be a way to switch between windows and tiles, but not tabs. Many other programs besides browsers use tabs. Even some DOS programs make their own tabs.

>> hope future browsers will let me opt out of their own
>> tabs easily.

Try searching for "disable tabs" and your browser name. Note the method might be version specific. I am not sure if chrome has an easy method, but I think that it is open source.

[disable tabs firefox] http://www.google.com/search?q=disable+tabs+firefox
For another browser substitute its name for "firefox".

> What do you mean by "operating system tabs"?

MS Windows, for instance, has something conceptually similar to browser tabs... it lists the programs and allows you to switch between them. Apps use either SDI (single document interfaces) or MDI (multiple document interfaces)... SDI windows can be closed with Alt-F4, and switched between using Alt+Tab... In an MDI the individual program-internal windows can be closed with Ctrl-F4, and Ctrl-Tab for switching between them.

I once posted a picture here showing tab recursion, not quite sure now what I called this post though!

>> hope future browsers will let me opt out of their own
>> tabs easily.

> Try searching for "disable tabs" and your browser name.

Firefox lets me do this. Just to clarify, I meant to say "... hope future browsers will *continue* to let me opt out ...". Chrome also has a sort of nice approach way to not get tabs much in the way if you don't use them (they're not completely out of the way though, e.g. they're placed first in the link context menu).

After reading this discussion I remembered that I was arguing the same thing awhile ago on the gnome shell mailing list and I thought it was relevant enough to copy it here:

== START QUOTE ==

Since the alt+tab discussion I have been thinking about the differences and evolution of windows and tabs and I have come to the conclusion that tabs should be something handled by the OS (window manager) rather than individual applications. Take a look at IE (despite everybody hating it, please leave your prejudices for now), they didn't want to integrate tabs, because the taskbar should have been responsible for switching between 'windows'; The Problem, the taskbar took an extra click as it was nested and uncategorised as you couldn't drag/drop and it's order was by creation. Below there is a list of arguments, advantages and brainstorming and at the end I wrote a system how this could be technically achieved.
*The difference between tabs and windows will fade
**Tabs can be visible in the alt+tab interface (and if nesting would be removed as I suggested than this would make it extremely easy to browse through tabs)
**Tabs can be integrated directly into the gnome-shell
**Loosing a tab is extremely common for hardcore multitaskers and if I am not incorrect gnome-shell also allows searching through windows
*Logical user interfacing: Tabs are logically placed (e.g. in google chrome) together with the other window buttons (_ [ ] x).
**Right now, if you develop an application (I am in general a web developer, so correct me if I am wrong) it's extremely complicated to create such an interface, despite being extremely logical.
**Tabs should be above all the other toolbars, as the toolbars actions always only have an effect on the content of the tab and rarely on all tabs at once.
*Allows grouping (potentially an extremely exciting feature, but definitely not a main feature.)
**Imagine dragging the a graphical app window into a browser window with tabs which are related, just like you can drag and drop tabs in Google Chrome.
**It can be argued that this is already provided by the workspaces, though I think the advantage of tabs is that you have a logical to the point taskbar.
*UI customizability/fluentness
**Any plugin/program could change the behavior of all tabs, rather than only for a single application like firefox
**Try dragging a tab in firefox from one window to another and check how problematic it can sometimes be (only chrome really handles it fluently), this mainly shows that even for a huge product like firefox it's hard to create a good interface, as an application is looking from the window level up, while gnome-shell could easily create such an interface as it is capable off looking down on all windows at once (if that didn't make sense ask and I will try to explain it with better words)

Technical implementation
*Application with tabs would be set up to work with single windows just like IE6 and below, this is definitely a option with firefox which could be the default browser using this pref.
*Next comparable windows would be grouped into tabs just like Google Chrome
**First a custom per-window based type-option would be checked which can be set by developers (not sure how or which product is handling this part)
**If not available the system would check windows of the same application with a certain amount of similarities, as preferences should for example be opened in new windows
***'Random' window information I have seen in compiz sometimes
***Window titles
***Size
**A blacklist should be checked where anybody can add applications for which it is illogical (which should naturally be moderated) (I could create the web-side of this)

You might have already realised that I am only referencing browsers, as I am a webdeveloper and I think browsers are forced to evolved most to keep up with the rapid progress of the internet and thus are an important example to look at. Aside of that I typed this up in a bit of a rush, so some of my arguments may not make perfect sense and my english may be messed up (I am not a native speaker, so that might contribute as well). Feel free to ask and please criticise the idea as much as you can, as criticism is the best way to improve an idea.

=== END QUOTE ===

However this idea was totally killed by the other developers and the fellow people on the mailing list (http://mail.gnome.org/archives/gnome-shell-list/2010-March/msg00098.html), but this is kind of what some of you would want as well, right?
  

Firefox 4 Beta 1 candidate build released

http://www.neowin.net/news/firefox-4-beta-1-released

I installed the beta and there is an option to place the tabs back to the old position after the navigation bar.