In Chicago style, when a source does not include page numbers but you still want to point the reader to a specific point within it, an alternative locator should be used in your note or in-text citation. With audiovisual sources (e.g. films, videos, podcasts, songs), this is a timestamp, e.g. 1:15:28.
Web pages are usually short enough that no specific locator is needed. However, for a particularly long web page, you can use a subheading from the page, in quotation marks, e.g. “Citing Sources with Notes.”
Note that page numbers should be left out of newspaper citations, even when they are available. This is because page numbers can vary between different editions of a newspaper.