Information is freely available via the Internet, but this does not mean it is free to copy and is still covered by specific copyright laws (generally the same principles and legislation that cover printed works). Unless explicitly stated otherwise, the majority of such resources will be subject to copyright restrictions and will be the property of the copyright holder. Even if there is no copyright statement on the material, one must not assume that it is copyright-free.
Hyperlinks to external websites do not usually cause any problems with regards to copyright legislation and principles. However, they should be incorporated in a way that ensures that the user is aware that they are being taken to an external site, and that the links does not suggest that the user is being taken to another page of the current site. With this in mind, a link should never be put directly on a navigation element of the page, as this could be considered ambiguous. Links should also be to a home page rather than deeper into the site. If the link is to a specific article, it should be made clear that the link is taking the user to an external site. Problems can also arise if an external site is linked or referred to in a derogatory manner, by quoting out of context or making an inference that is not directly supported by evidence.
Images on the internet are not copyright free, and care should be taken in their use. Designers should always strive to produce/obtain original material themselves. If necessary, images obtained from the internet should be purchased directly from the owner, permission sought from the owner, or copywright free images used instead (by using advanced google search or Creative Commons search engine). For any images used that are not your own, always acknowledge your source, and never alter the image unless permission has been specifically granted for you to do so.
There may well be multiple copyrights in screenshots, including fonts, graphics etc. If using these for learning and teaching purposes you must avoid any alteration to the original, and any misleading labelling.
Care must be taken with use of company logos, particularly where these are used to click through to a web page. Such use, without permission, would infringe the company’s trademark. There have been several high-profile legal suits resulting from such uses.