In writing my autobiography, is it okay to incorporate material one sees on the Internet if there are no conditons such as; “cannot be copied, etc., without the author’s permission?”
Unfortunately, lots of website owners illegally copy content from other websites, believing the entire Internet is the public domain. It’s not! You might find something on a website that the owner says (or doesn’t say) you can copy…but that content may have been copied illegally from somewhere else.
Somebody owns the copyright to everything created (since copyright law was enacted long ago), even if they didn’t register that copyright.
So, long answer short, no, you can’t republish something just because a website doesn’t contain specific conditions for doing so. Always get permission. If you can’t get permission and/or if you can’t find the real copyright owner, don’t use it. If you are caught, you could be sued. Even if you’re never caught, it’s unethical. We creatives know, perhaps more than others, how valuable our creativity is. Taking the fruits of someone else’s creativity and using it for profit is just plain wrong.