When I talk about mobile users' needs being different, what are the implications? Let's consider a fairly simple example: a corporate expense reporting application.
The typical use at a desktop is to assemble an expense report from receipts and perhaps automatic items, such as travel expenses. The user creates and names an expense report, adds and categorizes expense items, and submits the expense report. The main page ought to have a list of open (unsubmitted) expense reports, a button to create a new report (or even a form right on that page), and a list or access to a list of submitted expense reports (most recent first).
The typical use from a mobile device is to enter whatever expense is currently being incurred. Other use will be a distant second. Thus the main page should be a form to enter a single expense, as easily as possible.
The user need not enter the name of the business, just the category picked from a list (the name can be added later at the desktop). The expense can be assigned to an existing expense report, or no report, or a new report (user will have to enter at least the name of the report on a subsequent screen).
At the bottom of the form is a button labeled "Save", which will take the user back to the same page with a success message at the top of the screen. The expense is saved either to a report or to the "automatic items" mentioned above.
Because a small percentage of uses will be for some part of the main site's functionality, this is provided via a link on the page.
Bonus feature for mobile: based on the user's location and the expense category, provide a list of possible businesses to be receiving the expense.
This design, based on the users' needs in different contexts, can not be achieved by simply indicating which parts of a page should be published to a mobile.