We don’t really call the Internet the World Wide Web anymore, but we do still write a lot of web-related words.
But Web is capitalized when referring to the World Wide Web in short form. For example, Web page, Web feed or the Web.
My advice for remembering what is what is to use the more common, modern terms and make them one word. Because, after all, it’s always acceptable to write around a word when you aren’t quite sure about the appropriate usage. Or, you can look it up in your AP Stylebook.
Also, as noted above, Internet is uppercase.
I hope this helps you when writing techie, web words. Now go forth and use words correctly!