Defamation cases and the internet have been comfortable bedfellows, particularly given the proliferation in user generated content on the internet. The internet affords the average person (and the commerical publisher) the ability to insult any number of people with the least amount of effort. Defamation is regarded as a necessary qualification of free speech: you can see what you like about someone, as long as you are willing to be held accountable if what you say is defamatory.
The law on defamation in the UK has changed a little in relation to the developing technological landscape, but many of the fundamentals of the law of defamation haven't changed in quite some time. Several Victorian and early 20th century cases have influenced how the law applies in an internet context. One effect of applying these historic tests to publishers of material on the internet has caused particular concern, that of multiple publication.
If an allegedly defamatory statement is published, the wronged party has one year from the date of publication to bring an action against the relevant wrongdoer, under UK law. This limitation period enhances legal certainty; if a statement is published and nothing has happend within 12 months, no cause of action can be initiated against that particular publication.
The peculiar problem on the internet is how long statements linger. If a web page with a defamatory statement is published online, it is usually accessible for quite a long time. The Courts here have applied the traditional rule; 'publication' takes place every time material is made available, with no exception for materials on the internet (see Loutchansky below).
This is not great for online publishers, as it means potential liability for a defamatory statement for an extended period. The Times recently asked the European Court of Human Rights to look at this. The Times' view was that this extendable limitation was an unreasonable restriction on free speech, as protected by article 10 of the European Convention on Human Rights. The European Court of Human Rights disagreed, hence someone can still potentially be liable for defamation in the UK for publication of a defamatory statement more than a year after it is first published.
I think this is pretty unfair as it means online publishers are subject to the degree of uncertainty that a potentially indefinite right of action creates. I also feel quite sorry for the Times, who were the unsuccessful defendant in one of the main cases on this point of law in the UK, Louchantsky v Times, and then lost before the European Court of Human Rights when citing the same case.