http://news.bbc.co.uk/1/hi/uk/7586801.stm
Can anyone figure out if these guys did anything? Apparently there was no plot in place...Just a statement on their website. I presume it would be illegal to visit their site. I can only guess this "article" they speak of is a PDF document in their browser cache.
Makes me want to security wipe my cache on a daily basis.
What makes you think that this is "a PDF document in their browser cache"?
The web is built on a client-server architecture. The document was allegedly found on a web
server that they controlled, but if that was a web server with uncontrolled access for HTTP GET requests (like almost all web servers, that being the point of the web) then simply having done an HTTP GET for said document means nothing, given that the contents of the document (or more precisely resource, said document being the content provided by the Uniform Resource Locator) cannot be known until said resource is retrieved by the client.
The evidence against these people is not that their
client software had a cached copy of something published on a server, but that they
published something on a server. You have it down in your own description: "on their website". That means it's there on a server that they control the content of, and if they published it there, that can be seen as evidence against them.
If for some reason you end up visiting said web site and downloading said document, that's not your fault - any prosecution based on merely having a
copy of such a document on the client, as opposed to supplying the
original document on the server, relies on proving that you actively and systematically sought such documents, presumably for the purpose of furthering the aims of terrorists.
Although if your skin is of a darker shade than that of Action Man or Barbie, you may want to clear your cache anyway, as the Courts seem to have a problem understanding this.