Mobile and PC users can have different reasons for visiting the same site. Mobile users are more likely to want information to help them at that location or time, such as finding directions or finding out what's going on nearby. Also, they might want quick entertainment to pass away a short period of time, like something to read on the bus or while waiting to meet a friend. For your site, predicts users' needs and fulfil these as quickly as possible. Exceptions to this are items people download to keep on their phones (e.g. buying ringtones). Yahoo! does this effectively with its new mobile oneSearch TM service. Searching for 'Cinema' produces a list of cinemas near users' location showing their address and phone numbers. Clicking the 'Call' link next to a number opens a call dialogue box on the phone. A further enhancement would to be enable users to click through to a map of a venue.
Usable websites designed for PCs usually repeat the navigation on every page. However, screen real estate is precious on a mobile screen and navigation can push content off screen. BAA's navigation, for example, takes up the whole screen so users have to scroll down far on every page to get to the main content. For your website on a mobile, only display the navigation on the homepage. On other pages only include links back to the homepage and back to the last important point along the path users have taken. Show these links at the top and bottom of the page so they're never too far away.
Mobile phone users tend to have poor cursor control. This is because moving the pointing device down (with the joystick or direction buttons) simultaneously scrolls the page and highlights links, buttons and form fields. Due to this lack of control it's important to clearly feedback to users what item is in focus. This can be done by changing the appearance of an item to make it stand out from everything else. For example, you can change the font and background colour of links and buttons. For example, O2's mobile portal doesn't highlight buttons well. It adds a blue border on a lighter blue background that isn't noticeable. Users have to move the joystick around to find the cursor. Worse still, Thomson Local only distinguishes form fields by making their border slighter thicker. In contrast, their highlighted links stood out because the font and background colour was changed and contrasted strongly against the page's overall white background. O2's highlighting needs to be stronger to be noticeable.
Allow users to input information by making selections instead of entering free text (or at least provide this as an alternative method). Entering text on a mobile phone can be painfully slow and error-prone on the typical 12 button mobile keypad. Mobile users are more likely to make mistakes (due to misspelling or mistyping) or take shortcuts. Sets of well thought out links on quick loading pages can be very usable. On Thomson Local, for example, it isn't possible to browse businesses or locations. Users tend to abbreviate search terms (i.e. business type) which leads to inappropriate search results. The Odeon's mobile site allows users to find a cinema by searching or browsing. Users that search often make more mistakes than those that browse, the latter usually finding what they're after by only selecting 2 links.
Mobile phone screens are of course tiny and have only a fraction of the area or pixels on most PC monitors. Be sure to identify page requests coming from mobiles and only send down the most essential of information. Otherwise, important content might be pushed down or difficult to find amongst everything else on the page. Also, most mobile phone users aren't on flat rate data packages so the larger the page the more users have to pay. Users become frustrated if they have to pay to download page content they don't want. Header links on the BAA and Thomson Local websites take up lots of screen space and make important information hard to find. 'About BAA', 'Help' and 'Advertise with us' aren't priorities for mobile users.
To save screen space, mobile browsers often don't display basic controls such as 'Back' or they display the web page in full screen mode. As such, always include a 'Back' button on every page other than the homepage. Transport for London's mobile journey planner places basic controls, such as 'Next page', 'Back to results' and 'New journey', at the bottom of each page.
On your website, make sure you design the page to present content in the right order and render well on mobile screens. Website layouts for large landscape PC screens usually don't work well on small portrait mobile phone screens. Furthermore, mobile browsers and page transcoders usually vertically stack pages suitable for portrait display. It's often best to have completely different page designs to meet mobile users' needs. If mobile phone users are a big part of your business then you should consider creating a site just for mobiles . Sites that are designed for mobiles perform significantly better with users than those that aren't. For example, BAA's website renders very poorly on a mobile screen. Page sections don't appear where intended relative to each other and pages look poorly designed. Single word link text can be wrapped over 4 lines making it difficult to read. Conversely, Transport for London's mobile homepage contains simple categorised lists of links. Users find this easy and quick to use.
Seven usability guidelines for websites on mobile devices