Well I hope we're going full Luddite, because clearly the only right way to do comics is by hand traditionally and none of this disgusting modern digital art. And is it really a comic if you're posting it online anyway? Sound fake.
If you're going to print it, sure number it, it saves you a job later, although some services will number the pages for you. Lots of complied manga have a table of content so you can find the chapter, even though I know no one who would use it rather than flick through to the chapter, and that's if they're not just reading all the way through. Plus, if you're doing more than one book you'd need to go are renumber them again, since most collected manga would only have 5chapters at most in a book and I'd imagine a collected webcomic would go for something like the same depending on lengths. And that's if you've not added or rearranged the pages and panels in the editing process.
That said, as a reader, I don't care. In the chapter titles it can be useful if the site doesn't remember where you left off, but on the page itself, I couldn't care less, if it's there or not I doubt I'd notice or care.