The idea of splitting the browser's content window into panes isn't a new one. Konqueror, for instance, has had this feature for a long time.
What is Split Browser good for? Web developers should find the extension particularly useful, because it makes it easy to eyeball two or more sites side by side. It's also useful if you have a Web site like Gmail that you want to be visible at all times.
The Split Browser extension is available via the Firefox Add-ons site. Click on the Install Now button, and you'll be walked through the installation. Restart Firefox, and you should see a new menu, Split.
Using Split Browser
The extension is pretty straightforward, so it shouldn't take long to get the hang of using it. Click on the Split menu, and you will see all of the operations relating to the Split Browser extension.
Depending on whether you have any windows split, some of the options will be grayed out. If you right-click on a page, you should see an option in the context menu called "Split browser to." This allows you to split the browser window and choose which direction you wish to split the window -- to the right, left, up, or down.
Another way to split windows is to hover the mouse near the edge of a window, within the frame that displays the Web page. For instance, if you hover the mouse on the left side of a window, you should see a button with an arrow appear after a short interval, with a tooltip that says "Split to Left." Click that and the window will split to the left, and the current page will be displayed on both sides. Note that the arrow appears in the middle of the frame, not necessarily where you're pointing the mouse.
Once you split a window, you'll see a title bar with the title of the page that's being displayed, a red button to close the window, and (if it's enabled in the preferences) a show/hide button to the right side of the display. If you click on the title bar, it will change to a location bar with the URL of the page being displayed, navigation buttons, and the close and show/hide buttons on the right side. You can hide the split window so you have a better view of the other page(s) being displayed.
To open a new page in a split window, right-click on the link to the page you want to open. You should see a Load in split browser entry in the context menu. Here again, you have the choice of opening the new page on the left, right, below, or above the current page.
You can also "tile" windows using the Split Browser extension. If you have tabs open, you can go to Split -> Tile all tabs, which will open all tabs in one split window. If you want more control over how the tabs are laid out, you can use Tile all tabs horizontally or Tile all tabs vertically instead.
Split Browser is great by itself, but if you team it up with Fullerscreen, you can really make the most of Firefox.
If you have both extensions installed, you can press
If you've been reading a few pages in split windows and want to open those in tabs instead, you can go to Split -> Gather all split browsers here as tabs, which will open each split window in a tab and close the split windows.
You can tweak the Split Browser extension further by going to Tools -> Add-ons. Select the Extensions tab, highlight the Split Browser bar, and select Preferences. Under Preferences, you'll see three buttons -- General, Appearance, and Menu. Under the General tab, you can modify whether Split Browser saves its state (so new browser windows include the split), whether the Split buttons are shown at the edges of Firefox's content area, and whether tabs are closed when they're split into a new browser. The Appearance tab allows you to control whether the toolbar is shown in the split browser, and whether the Collapse/Expand button is displayed in the split browsers. Under the Menu tab, you can add or remove items from the Firefox context menu, and decide whether the Split menu will be displayed.
The Split Browser extension does have a few problems. For one thing, even when the split window has focus, if you try to reload a page or navigate backwards or forwards, the operation will happen in the original window. So, for example, if you split a page and try to reload the "split" page, the original page will refresh rather than the "split" page. This is seriously counterintuitive.
You can navigate using the toolbar at the top of the split page, but it's sometimes difficult to get the controls to appear rather than the page title. This also means that you don't have access to your bookmarks in split pages -- only in the main page.
The additional toolbar in split windows takes up valuable screen real estate. I'd prefer to see the Split Browser extension work the same way that Konqueror's navigation and location controls work, where the controls work with whatever part of the screen has focus.
Speaking of screen real estate, many pages do not display well in small windows. This isn't a fault of the Split Browser extension, but if you're going to be using Split Browser to view multiple pages in Firefox, it helps to have a monitor with a resolution of 1680x1050 or better.