Is copying any article's url or a webpage url from the internet and pasting it in Google Plus communities illegal?

Answer 1

No. Linking to content via a URL is generally legal, and the preferred way to reference content that is owned by someone else. What is NOT OK is copying content owned by someone else and using it as part of your own page. This includes, words, music, images and video. While "everyone does it" it is a copyright violation and is illegal.

There are exceptions. Many websites have Terms of Use that specifically exclude the practice of "deep linking", that is linking directly to content, rather than going through the content owner's home page. This is especially true with commercial news sites that typically charge for content. Several courts have ruled that deep linking without proper attribution is not "fair use" and is a violation of copyright law.

If you're going to use a URL to link to content that is owned by someone else, be sure to note the ownership of the content along with the link on your site. If you try to pass of someone's content as your own, you're asking for trouble.