Copyright Law
Material may not be coped even if there is no stated copyright. Just because you didn't see the copyright notice, does not mean that the copyright is not there. Ignorance is never an excuse for breaking the law.
Another myth about copyrights is that you can never get cought because you are innocent until proven guilty. Copyright laws are usually settle not in a criminal court, but people usually get sued instead in a civil court where the idea of innocent until proven guilty is not the motto.
Some people have the idea that if they don't charge for material, then it is not violating any laws to share it. This is a fallacy. Just because you have been given a copy of something does not make you the copyright owner, so you have the right to hang it on your wall, but if you post it to your website and share it (even for free) you are in violation of copyright laws, and those laws can be very severe. In fact, breaking copyright laws can be a felony and can have huge, huge fines and years in prison. It's not worth the risk. If you are going to use something you didn't make, you need to ask permission and give credit.
Images and songs are not the only things that cannot be copied without permission. Text is also copyrighted. If you find a lovely article online and you copy and paste it, or even re-write the exact same thing in your own words, then you are breaking copyright laws. It's called plagiarism and has been a crime for years. It can ruin your reputation and is just plain wrong. If somebody else makes something, you need to give them due credit.
Copyright laws are a key to a productive society. If copyright laws are not respected in a society, then there is little reason for people to come up with new better things. If an artist cannot profit by his because it is always copied for free, why should he paint? If Taylor Sift cannot sell her music because everybody shares it for free on the internet, why will she continue to produce new music?
Obeying copyright laws is clearly the way to go.
How I followed copyright laws in my website.
On my website I thought that it would be neat to play some background music, but I am not much of a producer of music and did not get permission from anybody to use their music on my website, so I refrained from using it. There were some neat headers on other websites out there which it would have been easy to copy and use as my header, but that's breaking copyright laws, so I didn't. I used an open source image editor, created my header myself and gave the image editing software company credit for their help in my learning report.
Each one of my learning reports, I did not come up with the ideas myself. I used other website as inspiration and used their instruction to add new features to my website, so I gave them credit and posted the address of their tutorials. I did this even though I had developed my own material for my website, but I did so copying techniques that others had developed and they deserve credit for their work.