The information on how to change the page format is wrong in the manual or the corresponding menu items are missing in my LibreOffice Impress version. The menu items do not exist as referred to in the manual.
I cannot find
I assume the correct location is
Slide->Page/Slide properties (which is moderately intuitive, I would look under "Format" to change a format...)
Build ID: 1:5.1.3-0ubuntu1
Yep, the docs need to be updated. https://help.libreoffice.org/Impress/Format
Now sure about "View->Web", but the page formatting should be up to date now:
Good point, I will close as dupe.
I don't know about View - Web either. There is only File - Preview in web browser.
*** This bug has been marked as a duplicate of bug 102265 ***