Already even owners of unconnected PDAs are using the Web via services such as AvantGo, which as well as providing direct connections for wireless enabled PDAs also support automatically downloading content to a PC and synching it to appear in the AvantGo browser on your PDA.

Second and third generation mobile networks will take PCs completely out of the loop, making PDAs many Web users' primary point of contact with the Net. Datacomm Research predicts 350 million PDAs sold by 2003.

PDAs provide more opportunity for content delivery than WAP-enabled phones. To fulfill their primary function efficiently, mobile phones pursue a different feature set from PDAs. As one of the main design aims for mobiles is ever-smaller size, Net access is compromised beyond common sense, making them an unattractive Net access option.

As we move toward dedicated - rather than general purpose - computing devices, PDAs look a far better bet for general Net access than mobile phones.

PDAs have more computing power, longer battery life, more built in storage and bigger screens. They are designed primarily for information storage and display - quite different design goals to mobile phones and much better suited to the needs of Web users.

Limitations

On the downside, PDAs still present problems from a Web designer's point of view. Compared with a PC, a PDA screen is small, its computing ability and power supply limited and its internal storage just a few megabytes at best.

For keyboard-less devices, screen sizes vary from the mono 160x160 pixels of the Palm IIIs to the colour 240x320 of the Journada 540. Include handheld PCs such as the Jornada 690 and screen width grows to 640 pixels but remains just 240 deep. The Psion 7 manages a 640x480 colour screen - which five years ago was, astonishingly, the design target for most Web sites.

In practice, handheld PC users can access many standard Web sites successfully, but may still have problems because they can't use full featured browsers. Netscape, for example, has an impractically large 10MB footprint.

Some PDA browsers attempt to present standard Web pages in a PDA-friendly manner, but this is a kludge. If the site is using tables, frames, cascading style sheets or Microsoft's CDF, it probably isn't going to display in any useful manner. AvantGo's Web delivery service is an improvement but only with its own browser.

The only fully workable solution is to design Web pages specifically for the target devices. In many ways this is easier than designing PC oriented Web sites.

Time Machine

Designing effectively for PDAs means forgoing graphics - including banners and graphical text - dropping tables, Java, ActiveX, and content mediated by plugins such as Shockwave and Flash. JavaScript can be used with many PDA browsers but it makes sense not to rely on it just yet.

Think in the same terms Tim Berners-Lee did when he first invented the WWW. Your primary tools are free flowing text and hyperlinks mediated by HTML.

Consequently, your most important creative effort goes into content choice and its organisation rather than presentation. In real world terms it's like moving from a house to a mobile home. You simply can't take everything with you but on the other hand, you can live comfortably with the constraints as long as you accept them.

Device limitations mean Web content for PDAs must be functional rather than decorative or entertaining. Functionality precludes frivolity - unless your service is delivering jokes, perhaps. Stick to text-only content with graphics limited to navigation icons. In fact PDA content lives or dies on two major issues: content relevance and the ease with which you can navigate to it.

Marshall McLuen was wrong. It's the message, not the medium, which is important. Remember, most PDA Web users will be asking for information. Concentrate on getting the information across. Layout, creative use of white space and clever typography simply get in the way. KISS - Keep It Simple, Stupid - always applies.

Relevance means making every word count. Doing this for a variety of devices all with different capabilities effectively means composing pages for the lowest common denominator. To reach the largest audience you have to assume your target platform has a small, mono screen and supports only a basic subset of HTML.

How It Looks

One important aid to the PDA Web page design process is POSE, the Palm OS Emulator available for the PC. You can download it for free from the Palm site. It enables you to see what your pages will look like as you compose them without synching them to a real Palm first. And, if your pages work on the Palm they should work on just about any PDA.

As information delivery devices, the constraints imposed by PDAs extend beyond screen size. In general, they do not support a choice of fonts. Most don't support colour. Text emphasis is usually limited to bold and perhaps a single larger font size. You have to accept this. For users it can be a positive benefit. Pages tend to be fast, informative and easy to read.

OK, you've pared your content down to the essentials, created pages as concise as Rolodex cards and as lacking in frivolity as a Quaker's dining room, but even the average Web page menu is too much for many PDA screens.

Smaller pages means navigation on PDAs is more hierarchical than on PCs. However, cascading menu screens can be tedious and confusing for users. How many of your co-workers can be bothered to learn to navigate the menus on their mobile phones? If your menus go more than three levels deep you're going to lose much of your audience.

Forms

A major factor in delivering the required content efficiently is to make heavy use of forms. All PDA browsers - including AvantGo's - support them because they're the simplest way of short-circuiting menu hierarchies. Forms can be used to supply a relevant menu or item of information directly from a keyword or phrase.

Of course, an alternative is to provide content in different forms for PDAs with different capabilities. This is difficult at the moment, though AvantGo offers a proprietary solution. In practice, it's currently better to let the user choose a version of your site best suited to their PDA. Naturally, you won't want to maintain multiple sites manually - that's what computers are for - but it means this isn't a good option for those with limited resources.

When suitable browsers become available, XML based pages will remove some of the limitations from PDA content delivery. With the intelligence in the browser itself, PDAs will be able to easily extract and format relevant content from a universal XML based page. However, it seems unlikely this will happen before you're called on to create PDA friendly pages. In the meantime, keep your thinking small and precise.