How Web 2.0-aware Are You?
Given the New Yahoo! Photos has launched (and an article I contributed to has been published, see 10 Cool Things About The New Yahoo! Photos), I have had a bit more time and energy available to put towards some personal and fun side projects.
The Web 2.0 Awareness Test! ;)
How Web 2.0-aware are you? Take the test here. Best viewed with a sense of humour (and headphones!)
The point of this was to light-heartedly poke some fun at the Web 2.0 meme, while also demonstrating a way of exposing whether or not specific URLs have previously been visited by the user.
Effectively, using CSS' :visited pseudo-class, one can assign a rule to links - for example, a red colour, specific background, height or other attribute. Links can then be written out to the document and will inherit these attributes if they have been previously-visited.
Javascript can then be used to test for matching attributes - whatever was set in the :visited CSS, effectively.
Isn't this kind of Evil?
As mentioned on the test page, a good technology can almost always be used for doing evil. I wrote this for demonstration and entertainment purpopses, but there's no reason someone couldn't use a similar approach with more dubious intentions - for example, shady marketers might be interested in determining if you have recently visited a competitor's site, and could take some action based on that information.
The technique is not new, having likely been technically possible with the introduction of the first 5th-generation browsers. Whether or not it will be fixed in future browsers has yet to be determined (see mozilla bug below.) It's possible browsers could be set up to deny javascript access to style properties on links pointing to external URLs, but that sounds almost excessive.
In general, the web is not generally considered to be a "safe" place - so surf with caution.