As your notebooks grow and change over time, you might want to delete pages or subpages that you no longer need. You can easily remove pages from your notebooks using OneNote Online, but be sure that you really want to get rid of them — Page deletions are permanent.
Important: Unlike the OneNote desktop app, where you can use Ctrl+Z to undo actions, deleting pages in OneNote Online is immediate and permanent and cannot be undone.
In OneNote Online, go to the section containing the page or subpage you want to delete.
Right-click the page title, and then click Delete.
Acknowledge the warning that appears, and then click Yes to delete the page.