A copyright mention in a footer of a website means you can't copy any of the elements on said website. Not the texts nor the images. However your have some rights to quote a website. It must be evident that it's a quote, you must attribute it, it's good to link to the source. The quote must be small in regard of the original content (not all the original content).
Some sources allow you to reproduce anything from them, like Wikipedia. On Flickr, you can make an advanced seach and target creative commons content that allows for re-use. Be aware that it's not the same if your site is personal or if it's a business. If it's a business, you must search for commercially OK licences.
@Crownife it's funny not long ago, one of my client consulted me if that letter he received (cease and desist) if it was legit. It turns out the claim is 100% legit. So there's nothing he can do but to remove all those images his previous web dev used. As for the COPY like product descriptions "of the product you're affiliated of " it's Ok to copy and paste.
I'm making a timeline of Bill Gates life, and....I used multiple sources to make it. I have the links to all of them, but now I gotta go back and check those links...and see if I am able to use their facts?