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undo split screen

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my screen is going into split screen & I don't want that....how do i undo split screen?

my screen is going into split screen & I don't want that....how do i undo split screen?

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Firefox doesn't have a "split-screen". Unless you installed an add-on to add that feature to Firefox.

Perchance is one of your Bookmarks opening in the Sidebar? If so, open Properties for that Bookmark {right-click and select Properties} and de-select "Load this bookmark in the sidebar".


That 'box' can become check-marked when using a "Bookmark this Page" 'button' on a web page; the JavaScript for that type of 'button' isn't fully compatible with Firefox. So don't use a 'button' on a web page to save a page as a bookmark, use the "Bookmark this Page" feature that is inside of Firefox instead.