Say you want to compare two HTML files, where one is a slight modification of the other. So you open both in Notepad++ and use Ctrl+Tab to flip back and forth between them to detect any differences. Let's also say each file is long enough that it takes three or four Page Downs to get to the bottom. So as you're flipping back and forth and comparing, you eventually need to scroll down or Page Down. If you try to keep each file at the beginning of a particular line of code, Notepad++ will NOT keep the pages stable when switching back and forth. It seems to move them around randomly, or puts them back at the very top.
Ctrl+Tab should keep the pages exactly where I left them.