Copyright infringement is very similar to plagiarizing. It involves taking other people's ideas without giving them credit, or even posting large portions of their work on your website or using it in some other, public way. Fair use means there are a number of words or a portion of another type of work (like a picture, etc.) that can be used without infringing on copyright. Using information available on the web can be a good choice to add to a blog or website, but it is very important to cite where the information came from. If it is possible to contact the copyright holder and ask for permission, that should also be done. If asked to take it down by the copyright holder, that should be done immediately.