Spelling in the Electronic Age
Is it Web site, Website, web site, or website?
It’s Web site and Web page.
Because Web is short for World Wide Web, it should be capitalized as a proper noun.
Most style books, including The Chicago Manual of Style, and most dictionaries, including Merriam-Webster, mandate the two-word spelling with Web capitalized. The same goes for Web page.
The Oxford English Dictionary, on the other hand, prefers a more progressive spelling: website.
Email, e-mail, or E-mail?
Either e-mail or email, depending on whom you ask.
Although Google and Yahoo use email, the New York Times and other authoritative publications prefer e-mail.
It’s true that American usage tends to drop hyphens over time (so decision-maker is now decisionmaker). But when a single-letter abbreviation functions as a syllable on its own, the hyphen remains: X-ray, T-shirt, A-frame—and e-mail.
Internet or internet?
Not much disagreement here. Internet is a proper noun and is thus capitalized. Even as an adjective—Internet source—Internet takes a capital I.
You can use internet, however, for any other network that exists between two locations.
Online, on-line, or on line?
It’s online or on line, depending on what you are doing.
When you log in to a Web site, for example, you must provide your login credentials. But you never login. Rather, login is an adjective, while log in is a verb.
Similarly, online is an adjective, while on line is a prepositional phrase. So, for example, you do online research to find cases on line.
Unlike e in e-mail, on is not a single-letter abbreviation, so the hyphen is not necessary.