From that article, the first thing mentioned is that: even if there is no copyright notice attached in that particular material that you found, it DOES NOT automatically mean that it is not copyrighted.
The rule of thumb is:
Whenever you are not sure whether the material is copyrighted or not, it is always safest to assume that it is copyrighted.This is especially so as most countries (including Malaysia) are signatories of the Berne Convention on international copyright law (currently the bureau in charge is named World Intellectual Property Organization, an organization within the United Nations).
Nonetheless, if you are like me, where you just love to share the materials that you have created, teaching notes that you have written, power point slides that you have painstakingly made, strictly for educational, non-commercial purposes and at the same time, you want to protect and retain some copyrights of your materials so that your "kindness" would not exploited, the EASIEST way to do so is to sign up for a copyright license under Creative Commons. In fact, creative commons allow you the flexibility to choose whether you would want to allow your materials for commercial purposes, whether modification of your work is allowed, the name and URL such work should be attributed to, etc, etc. By keying in the relevant information, within minutes, an HTML code would be automatically generated. Just copy and paste the html code in your relevant blog post or webpage. Click here to start using Creative Commons license.
To protect your images/pictures/diagrams, etc, etc, you can watermark your work with a copyright notice together with the URL such work is attributed to. The best is PicMarkr, this website allows you for FREE customizable watermarking (protecting) of your work.