Plagiarize! Plagiarize! Let no one else’s work evade your eyes!
Sure it’s funny there, but not so funny when you really do it. Or when someone comes after you because you stole their words or their photos. Just because it’s online doesn’t mean it’s free.
Everything is automatically copyright (and belongs to the person who created it), even if they don’t specifically say so.
There are some exceptions.
Public domain works
Copyright lasts 70 years. After that, it’s in the public domain (unless it’s renewed). You can use anything you like of Shakespeare’s, take your own pictures of the Acropolis (the builder can’t sue you), and photos that are in the public domain.
Creative Commons
Sometimes called “copy-left”, creative commons lets you create different degrees of copyright. Some are free to use if you attribute the creator. Others must be non-commercial (though it’s a bit unclear what commercial means – don’t use the image to illustrate a blog? don’t sell the image as a poster?). Another license lets you use the words or photos under a share and share alike license. This means you can use it, but whatever you use it for is also share alike (like Wikipedia). There are also lots of sources for free, legal photos.
Permission
You have permission. Sometimes, just asking will get you an OK to use something. If you want to use something of mine, just ask.
Fair use
This is a little tricky, but it essentially means that news organizations writing a story about McDonald’s can use a picture of the McDonald’s logo to illustrate their story. Or, a comedy show can use it as part of a spoof. You can also quote small portions of a copyrighted work (with attribution). If you’re going to sell something with the quote in it, you might want to get permission (like using a poem in your novel).
Note, I am not a lawyer. These are just general guidelines to keep you out of trouble.
Can you identify the quote at the top? Bonus points if you do.