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.
Caution: Unlike the full-featured OneNote apps, where you can use Ctrl+Z (Windows) or ⌘+Z (Mac) to undo your last actions, deleting pages in OneNote Online is immediate and cannot be undone.
In OneNote Online, go to the section containing the page or subpage that you want to delete.
Right-click (PC) or Control-click (Mac) the page name, and then click Delete.