Many websites are not at all friendly for visitors using mobile devices or tablet computers. The current craze for QR codes reveals that many website owners are being very lazy in this regard: when the QR code is scanned using a smartphone your are nearly always taken to an mobile unfriendly landing page. There are a few notable exceptions such as Rightmove where there is clever switching of presentation for mobile and desktop devices. An alternative approach is to design a fluid layout that looks good on a very wide range of screen sizes. This is the approach we chose when updating the Tech-Trends website to make it more mobile friendly. Many other websites could do with following the same process as us.
A good website design has the platform (webserver and supporting software), content, and styling completely independent of each other. This approach saves huge amounts of time in maintenance and therefore has strong cost implications for website ownership. So if your site is not built with a CMS (Content Mangement System) now is a good time to think about updating.
Make sure your site meets all the W3C standards. We display the W3C logo's at the foot of every page for a reason. If your site has code errors then all the time and money you have spent developing may be wasted. I have just been looking at the website of a blue chip company and found some of the pages are blank on my combination of cumputer and browser!
Use a simple layout. All our menus are generated automatically from website content. We have removed sidebars that do not work well on mobile devices to create a single column format. For articles we have made use of teasers to summarise the full content. We have also made good use of taxonomy (keywords) so users can easily navigate to groups of pages on related topics. If we ever decided to display a gallery of images we would use thumbnails of equal size linking to the full image as this works over a wide range of screen sizes.
Remember Content is King when it comes to the user. Most users visit a website to get something they want, not to admire the layout. An attractive content free website, or one with confusing menus only navigable with a mouse will win no friends in the new mobile browsing age.
A final note. If anyone claims that they can help you set up a mobile website, check theirs out on a mobile device and the W3C validator. One such we checked out had 86 errors and was very, very limited in capability on the mobile screen.