With vast volumes of creative content pouring onto the web every day, from blogs and photos to MP3 music and streaming video, copyright protection has never been more important. Sadly, it's mostly misunderstood and often ignored, but the principles are quite basic.

International law gives the creator of a piece of work the commercial rights to that work, and prevents others from using or selling that work without permission from the creator. 'Work' in this case can mean literary, artistic and scientific documents, representations, pieces of music or any other original creation that can be represented in a tangible form.

For example, a song can be copyrighted, in both lyrical (printed) and musical (audible) form. A book can be copyrighted and so can a photo, a film and a computer image, but an idea cannot. You can protect some ideas using patents, but copyright only extends to tangible creations.

What you may not know is that copyright law extends to websites, including HTML coding, Javascript functions and graphics. You may find it easy to right-click on an image on a website and hit Save, with the intention of using the same image on your site, but if you do so you are breaking the law, albeit civil rather than criminal law.

And it's not just UK law you're breaking. Copyright law is enshrined in the Berne Union for the Protection of Literary and Artistic Property more generally known as the Berne Convention. Signatories to this Convention include all the major 'developed' countries of the world. The law itself will vary from country to country, but usually only in minor ways such as the expiry date for a piece of copyrighted work.

Here we'll discuss how copyright law affects people running websites, in terms of what you can and can't copy from other sites and how you can enforce your own copyright.

Copyright basics
In most countries, including the UK, there is no need to register the copyright of your work with a central agency. Copyright exists automatically as soon as the work is created and stored in some form.

However, to prepare for any possible future disputes, it's a good idea to have some kind of proof that you created the work at a specific time. One of the most popular methods of doing this is to send a copy of the work to yourself via registered post, in a sealed envelope. Don't open the envelope when you receive it; keep it in a safe place and the postmarked, signed-for package will be your proof of copyright start date.

You can do the same thing via email, if you send or 'cc' the document to yourself, although you should make sure that it actually travels through the internet and isn't simply kept as a local 'sent' copy on your hard drive.

For example, the moment I finish writing this article and save it, my copyright ownership begins. When I email the finished document to the editor of PCW and 'cc' it to myself, I have date-stamped proof of the start date of my copyright, which is valid until at least 50 years after my death (the length of copyright duration varies for print, graphical, audio and film media).

PCW prints this article in the magazine under licence from me and pays me a copyright licensing fee for the privilege of doing so. If anyone infringes my copyright by copying this article for commercial purposes, including publishing it in other forms, I can take legal action against the infringing party for damages and costs. After the copyright time limit expires, the work is in the public domain.

Where websites are concerned, proving the creation date is even more straightforward. As long as the system clock on your PC - and, more importantly, on your website's server - is accurate, any file copied to it, directly or via FTP, will be given a time and date stamp. This is proof that the creation date for copyright purposes was no later than the date the file was uploaded. So it's relatively easy to establish when a piece of work was created and who owns the copyright.

Even so, it's helpful to include the copyright symbol, owner's name and creation date, to reinforce the point and to make people more widely aware of copyright issues.

The accepted method of asserting copyright in this way is to use the copyright symbol (©) or the word 'Copyright', followed by the date (usually the year will suffice, but for some fast-moving industries you might want to include the full date), followed by the name of the copyright owner, which can be a person or an organisation

What you can't do
With this knowledge in mind, it should be pretty obvious that one thing you absolutely cannot legally do is copy a piece of work from another website and publish it on your own site without permission.

This includes copying blocks of text, Javascript or other code, HTML structure (the tags themselves are not copyrighted, but any block of HTML code that produces a unique, 'creative' effect might be) and, of course, graphical images and photographs.

Internet browser software over the years has made it remarkably easy to copy text and images from websites. Arguably the developers should have been more thoughtful, because there are really very few situations in which such copying would be legal.

Resist the urge to copy anyone else's content. They will have spent a lot of time and/or money creating it in the first place and they deserve to benefit from that process, as do you when you create something of worth.

Another method of copyright theft is so-called 'page grabbing' or 'page ripping', where a server-based CGI script, or similar method, is used to grab some content from another site, surround it with HTML code that looks like your site, and then publish it dynamically. Tempting as this may seem as a way to get cheap (i.e. free) content for your site, it is illegal without the written permission of the copyright holder.

The above two examples are pretty clear cut: you cannot copy or republish other people's work without the copyright holder's permission. Other forms of content management are rather more grey in legal terms. One of these is the practice of linking to other sites' content by showing their full pages within a frame. Ask Jeeves still does this, but the practice is dying out as the target sites increasingly complain about it.

The usual method of framed republishing involves an HTML header from one site, beneath which is a frame containing the full page of the remote site. Initially this was grudgingly accepted because it at least showed the entire target page - advertisements included - but now it is believed that framing causes problems in two respects.

First, there's the loss of revenue due to a reduction in the impact of page advertising, because more advertisements reduce the effectiveness of each individual advertisement. Second, this type of publishing implies that the content is owned by the framing site, which is misleading and the framing site is gaining market respect by doing this.

Another grey area is deep linking. For example, instead of linking to www.wesellstuff.co.uk, you might link to www.wesellstuff.co.uk/products/videos. You might think that the target site would be glad of the extra traffic, and in some cases you would be right.

However, disputes are currently making their way through various international courts because deep linking could lead to a loss in advertising revenue for the target site. For example, in the above case, we have effectively cut out the 'products' category page, not to mention the home page. That could equate to lost page impressions per user, with the associated loss in advertising revenue.

As these two methods of linking could place you on legally unsafe ground, your best bet is to make sure you get written permission from the webmaster of the target site before including any deep links on your site.

Perhaps you're thinking that you could infringe someone's copyright and then quickly remove the offending content from your site if anyone complains, claiming it was never there. Think again. Copies of your site's pages are stored in caches held by search engines, users' browsers and non-profit organisations such as the Internet Archive.

Try as you might, you won't be able to delete every copy from the internet. Even if you did, the company hosting your site will have monthly, weekly or even daily back-ups archived away. The much-vaunted immediacy of the internet is a fallacy in this respect. Just as old emails can come back to haunt you, so you can never completely remove the traces of something you've published on a website.

If the case went to court, you could be found liable for backdated licensing fees and - what is likely to be more expensive - damages and costs. It's not worth the risk.

What you can do
You can use other people's material on your website as long as you have written permission (an email should suffice) from the copyright holder.

When this happens you will become a licensee of that copyrighted work. The terms of the licence will vary depending on what you and the copyright holder have negotiated, but usually you will have a single-use, non-exclusive licence.

This means you can republish the work once and that you do not have an exclusive licence, so the copyright holder is free to license the work to other people too. Generally you will not be able to resell the work to other people, since the copyright remains with the owner.

Usually you will have to pay for a copyright licence. The exact amount is entirely a matter for you and the copyright holder, and will depend on the value of the content to you and the value of uniqueness to the copyright holder; if their work is republished on many sites, they may feel it is commercially devalued as people won't be so keen to visit their own site.

There's plenty of scope for negotiation, though, and you may find that in some cases a link back to the originating site will be enough, particularly if your site has considerably more traffic than that of the copyright holder.

If you are licensed to use the work on your site, you should still - unless the licence explicitly waives this requirement - include the copyright symbol, the date of the copyright and the name of the copyright owner somewhere near it, so that it's clear that you are licensing the work.

Exceptions to the rule
There are some circumstances in which you can use another person's or company's work without a licence without infringing copyright.

For example, if you are reviewing, criticising or satirising it, you can include fragments to illustrate your point. Exactly how much you can include isn't set in stone, but the term for this sort of usage is 'fair use', which will give you an idea of what's involved.

A few seconds of music from a song, a few lines of a poem or a few paragraphs from a book are unlikely to cause problems, but republishing larger pieces from a work is likely to exceed the limits of 'fair', so you'll have to use your own judgement.

This is an area in which you might like to contact the copyright holder beforehand and let them know your intentions. Often they will be happy to let you use larger sections of their work if they think it will increase its commercial or artistic value.

Fair use also extends to education. Teachers can make limited numbers of copies of some copyrighted material for use in lessons and lectures. The terms vary depending on the item being copied; a good resource here is your local library, which should be able to tell you about the individual restrictions.

As a general rule, items with Crown copyright can be more freely copied than private or commercial works, but there are exceptions. Here again you should always credit the source and the copyright holder when quoting from or referring to such works.

Protecting your own copyright
Having gone to all this trouble to ensure that the third-party content of your website is legitimate, it's time to look at the other perspective: how do you protect and license your own original work?

Starting with the protection aspect, there are several steps you can take to reduce the risk that casual copyright thieves will steal your work. All have advantages, but they also all have disadvantages. Starting with images, one of the simplest things to do is include a piece of Javascript code on your pages that disables the right-click menu.

You can download such a script from various web repositories, such as Hotscripts.com (search for 'anti right click'). Embed this somewhere in your page and voila, your images are protected.

Except that they're not, of course. This won't stop people with Javascript turned off in their browsers, nor will it prevent users of non-Microsoft browsers from right-clicking, since the code is usually only for Internet Explorer. And it won't stop people doing a screen capture, either.

One other trick, if you're a reasonably capable HTML coder, is to overlay the image with a completely transparent gif of the same size, so that right-clicking only saves the blank image, but again this won't stop the dedicated, only the casual.

Perhaps your best option is to embed watermarks in your graphics files, something that can be done by Photoshop and Paint Shop Pro. This won't stop people copying your images but it will help you prove ownership if you find someone else using them.

As far as text content is concerned, there are two main methods of protection. The first again uses Javascript, this time to encrypt the HTML page content and the decrypt it 'on the fly'. This is useful for preventing people setting up automated page rippers to steal your content, but any competent programmer will still be able to overcome the protection without too much trouble.

A search for 'HTML encrypt' will produce a list of suitable programs, some of which work online and cost nothing. The levels of encryption vary from basic obfuscation to clever routines to prevent offline browsing, inward linking and code viewing.

A more effective solution is to serve your text content as a graphical image. Software is available to do this, although it tends to be expensive and usually sold as part of a large-scale content management system. It also raises accessibility questions and, like the Javascript option, prevents search engines from successfully spidering your site, at least without some kind of agent-detection system.

If someone contacts you and asks to license your content, it's up to you to negotiate a price and structure that doesn't reduce the value of your work. Copyright licensing contracts can be pretty simple affairs, but it might be best to get a lawyer involved to make sure you haven't missed anything.

Keep your licensing costs fair and reasonable to encourage more licensees and reduce the risk of copyright theft. Arguably it's the high licensing costs for published music that has led to such widespread piracy of songs via MP3 and other formats.

And remember, licensing only allows the other party to use the content for one purpose. They can't resell it or otherwise profit by it except in accordance with the terms of the licence.