Copyright
If you design, produce or write anything, copyright law applies to the end product. You don't need to be well versed in law to understand copyright implications, but a basic understanding could potentially save you wasting a lot of time, energy and money.
Copyright law exists internationally, but varies from country to country. As far as Websites are concerned, the images, any unique programming code AND THE WRITTEN CONTENT! are subject to copyright.
It is very difficult to apply copyright law to HTML or a design layout. Programming languages such as JavaScript on the other hand can be manipulated in many ways to produce many different events. A visit to www.javascript.com can show several ways to perform a task. Programmers upload there code for people to use, and all of it requires an acknowledgement to the creator to be inserted into the HTML. Also, some of it is for personal site use only, not commercial. Disregarding any instructions infringes the law.
To apply copyright to your site, all you need to do is to include the universal copyright symbol, ©, on the pages, the date of publication and the name of the copyright owner whether it be yourself or your company. Once applied, the copyright will last until 50 years after the authors death, unless abandoned or relinquished.
Once in place, the copyright notice is a declaration that you have permission to use all material or that you own the contents of the site. This includes images, sound, code, logos, text and most importantly the design. The exception is where you have permission to use someone elses content or design template, then the copyright rests with its creator.
There are many "free" images, animations, codes and templates available on the internet. The accreditation is either in the name of the image/code, or should be contained within comment tags.
DO NOT use a copyright notice when you use materials which are in the "Public Domain", that is - produced by the Government, or when you use "Fair Use" materials - material copyrighted but used for news, research, education or parody.
You can prove the date of origin because your computer gives the date of origin in the properties of a document, you can also save it to a disk and post it to yourself by recorded delivery, although for most sites the latter would be a bit over the top.
Basically - if you are in doubt, ask. Promotional photos of famous people are copyrighted to the photographer or the promotions company - Ask. As copyright law is international, you could be sued for breach of copyright in any country. Awards by American courts are prohibitive. That said, you will usually be contacted and asked to remove it or acknowledge the copyright.