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Skating on thin ice

Ajax has been called 'rollerskates for the web'. It's a fitting description because it makes things go faster, there's the risk of doing some serious damage and a lot of people don't know how to stop.

Even if you don't know the jargon, you'll know the effect: When an ecommerce site updates the shopping cart in the corner, or Gmail opens an email without clearing the screen, that's Ajax. It's about changing a webpage without refreshing all of it. The technique can create a more fluid user experience, with less of the stop-start associated with having a page refresh for every action. But it does bring problems of its own.

Because the browser's history stack is not being used, the back button usually fails. Clicking it could take the user several steps back in a transaction funnel, or could undo several actions when the user only wanted to rewind one step. Site designers should ensure that page refreshes occur at points where the user might want to 'save' their progress. Software back buttons can be added within the webpage, but users will still instinctively reach for the browser's back button and will be frustrated if they lose too much work.

Ajax can also prove confusing, particularly for users of assistive devices like screenreaders or magnifiers which concentrate on part of the page at a time. If updates are made to parts the user isn't viewing, feedback will be missed. Some have joked that Ajax stands for 'accessibility just ain't exciting' and it is still hotly debated whether you can use Ajax and still have an accessible website (Ajax actually stands for 'asynchronous JavaScript and XML' - see, you're pleased you asked now). Standards campaigner Jeremy Keith has developed a methodology called Hijax which is based on standard web navigation and form features, and uses JavaScript to hijack them when available.

The latest versions of the Jaws screenreader (version 7.1 and higher) can notify users of updates to parts of the page. Screen reader vendors are updating their technologies to keep up with changes, but it's expensive to upgrade and many users will already have an older version that doesn't support Ajax. 

There is a role for Ajax: it is particularly strong when used for form validation or for updating shopping baskets, and it can be accessible when Hijax techniques are used. Features like drag and drop (which are more difficult to make accessible, and which will never be accessible to some people, including those who cannot see the screen) can enable new online activities that ten years ago would have been unthinkable on the web. But it is essential that Ajax sites are fully tested with a wide range of users to ensure that they are accessible to everyone.

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