You do not need a special license or whatever to copyright it. It is no different in cyberspace. Any content that you create belongs to you! However, registering and licensing does have credibility. They are solid evidence that you did indeed create such things (and cared enough about it to pay money to register the copyright). In cyberspace, with so many forms of electronic input and output, it is more difficult to have solid evidence to show that you did create your stuff. One of the best things to do about this is to simply state in clear, legible wording that your content belongs to you and that nobody else has any right to use it or take it without your permission. For example, take a look at the bottom message at the end of each page of STOP.
What's Infringement/Plagiarizing and What's Not:
There are several forms of 'copying'. Not all 'copying' is illegal though. Downloading pictures, text, multi-media files and such for personal viewing and wallpaper or printing is perfectly fine. And even if it weren't, people wouldn't be able to control it anyways. Copying GENERAL facts and ideas are GENERALLY termed 'Ok' but copying or paraphrasing in the exact detail and sentences/wording is a no-no. Likewise common knowledge cannot be copyrighted. (ex. 'All humans have heads'). So to summarize this much, downloading to your hard drive is fine, storing files in your cache is fine, printing files is fine. But what isn't fine?
Suppose you were writing a report and you decided to use the Internet to research. Then you find somebody's social paper posted up, all perfectly accurate and presentable. If you copy it and hand it in as YOUR assignment, obviously, you are plagiarizing. Even if you copy passages of it or if you slightly modify the text. This is no different from copying text from a non-electronic printed source like books. Taking someone else's creation and claiming it as your own is definitely illegal. If you wish to quote directly, you MUST cite/reference your sources. (That means including the url from which you got it) Most universities will kick their students out if they are found to be plagiarizing off someone else and just because the professors are generally older, does not mean that they are not familiar with the Internet. If a student has access to something published on the Net, then generally the professor can also access it.
Some people may argue that because content is available in cyberspace, it is widely available to the general public and thus they can freely do what they want with it. WRONG! They are free to download and such for personal viewing but in terms of publicizing or usage; that is another matter.
It's simple. If you want to use something from someone else's site, just contact the webmaster and ask for permission to use it. Be sure to specify the exact material. Once you have permission and have taken it/used it on your website or whatever, make sure that you have credited the person for allowing you to use the material. You can either state it on the same page that you used the material on or create a separate page for credits and disclaimers. Make sure that you link to the site or email address of the person that you got it from.
An example of one would be like: "Credit goes to Mr. Nonexistant for allowing me to use his java applet. If you would like to use it, please go to his homepage: http://whatever.com and ask him first." More info on crediting/citation of sources can be found here.
Many websites, chatrooms, messageboards and the like are created in dedication, no doubt to certain interests of the creator. (ex. StarTrek). Now the things that these sites are based on may not necessarily belong to the webmaster/person. So can a person hold copyright over a subject that is not their's? This issue is very controversial. Suppose Mr. Nobody created a site dedicated to his fav. TV show: Ziggy Zaggy-Zipper. And so he wrote up profiles for each of the characters, wrote scenarios and summaries and edited pictures and posted them up. Now, suppose the creator and TV producers of Ziggy Zaggy-Zipper created their own **official** website and decided that they didn't want any fans to post up scenarios, summaries, profiles, pictures or sound recordings (etc.etc.), then they most certainly have a right over Mr. Nobody's usage of material from the show. Mr. Nobody would be notified and forced to remove his stuff from the show (particularly the summaries, pictures and sound) or else he could be slapped with a legal lawsuit. BUT, Mr. Nobody does have a right to continue his website basing it on his own opinions. He can review the different episodes and explain how he feels about it and other components. It all depends on the wishes of the legal creators and companies. As of then, Mr. Nobody's content solely belongs to him (since he did create it and not even the legal comany/creator can copy his content WITHOUT his permission, even if they do own the actual show). He also has a right to the EDITED pictures (ex. animated, transparentized. . .) although the overall copyright over the images still belong to the respective creator and companies. If the respective creator/company does not want Mr. Nobody to use any images, whether edited or not, then Mr. Nobody will have to remove his edited ones if he wishes to avoid legal hassle. Nevertheless, if people would like to use Mr. Nobody's material (eg. to quote some text), they still need to ask him for and receive permission first.
Also, since Ziggy Zaggy-Zipper belongs to someone else, Mr. Nobody should also include a disclaimer on his pages. On his main page at the very least, stating that he didn't own the show and such and that his page was for non-commercial purposes.
Suppose you downloaded something onto your hard drive that you'd like to use on your webpage, but you forget where you got it from. Consider the risks and follow your instincts. If you feel you _must_ use that file regardless of all else, state on your website that you forget who it (the file) belonged to and that if you were contacted by or alerted to the right owner/creator, that you'd credit that person or take it off if he/she wanted you to. This is not recommended because some other person could always pose as the rightful owner. To avoid such uncertainty, it's highly recommended to keep track. Some people find it helpful to use spreadsheets to do this. If you plan to use the material from an unknown source in a non-electronic median (ex. report/essay), consider the credibility it offers. A quote from Dr. So-and-so always lends more credibility than a quote from Anonymous.
The Rejection Process:
It's pretty obvious. 'No' means 'no' and if permission is declined, don't go ahead an use the file/data anyways. Believe it or not, this has happened before and has caused a lot of conflict which in some cases has led to legal cases. Just the same, if you've made a request but have not received a reply, the request itself does NOT grant you the right to use the item you want to use. Most owners/creators are very busy people and they may not be able to get back to your email right away. Give them a week before making a polite request again. If you still receive no reply in the following two weeks, then consider the answer as 'No'.
It's better to credit and disclaim or you may find yourself in the courtroom losing against a lawsuit. Coming from the other point of view, isn't it just easier to inform others of your copyright to prevent infringement from occurring in the first place?