But without specific approval from the copyright owner, you absolutely positively cannot legally publish any substantial portion of it for any purpose in any manner, most definitely including posting it on your web page. This would also include news articles published on the Internet by commercial news services such as AP, UPI, Clarion, or The Washington Post. Quoting anything more, especially in large quantities, asks for trouble. In other words, to cite extremes, the owner of a fundamentalist religious web site would not be happy to find his logo displayed on a site featuring erotica, even if used as a link to his site. If in doubt, ask first.
Theft is theft.
It's that simple. Registering it with the US Copyright office can later assist with such documentation, but that alone provides no other protection. Nobody, anywhere, will attempt to protect your work from theft. The purpose for and circumstances under which you used the other guy's property are of little importance. Theft is theft.