Offline differences

• Offline browsing: Relatively few mobile device users currently have a wireless connection, and many of those who do just connect via modem, sync their devices, and then disconnect and work offline.

This means that you must design a fairly tight chunk of pages to download with the home page. You determine which pages are downloaded from your site when a user syncs your channel by specifying a setting for Link Depth — the number of links from your home page within which your pages are to be downloaded.

You can also specify whether pages within that link depth, but outside of your website, are to be downloaded in a sync. Also, it is very important to avoid links to outside pages that are not optimized for mobile devices.

If you don't plan carefully, important pages may not be downloaded — either because they are beyond the Link Depth, or because the total size of pages exceeds the maximum size set for your channel. See Size limit issues.

• Offline form submissions: You must ensure that any forms used in your channel website do not require the user to wait for a response from the server after the form is submitted. Forms submitted offline are queued for submission to the server in the next sync. If it is absolutely necessary, you can prevent an offline user from submitting the same form again before syncing and getting back the server's response page.

In addition, you will probably want to set up special handling of form submissions to ensure that the user understands what has happened to the submitted form and can easily find the response page after syncing. See CHAPTER 7. Managing channel form submissions.

• Page hit measurement: In online browsing, when a user downloads one of your pages, you can't tell how much time was spent reading it, or if it was read at all — but at least you can be sure that the user clicked a link or entered the page URL to download the page. When a user subscribed to your channel syncs, your channel pages are downloaded, but that doesn't mean that user ever gets around to clicking through to any particular page. See Caching prevents me from counting user syncs for a good solution: counting user syncs. AvantGo offers a proprietary page tracking solution, which requires special coding in your pages. See 4. Promotions and page tracking.