In fact, there are considerably more mobile OSs and browsers for mobile than for than the desktop, and it's almost impossible to cater specifically to all of them. While you can custom-write an application for each one, this would be very expensive and time consuming, and wouldn't be very practical. Instead, you need to have a website that is browsable by all the different platforms. Many companies choose to have a mobile version of their site that is lighter and loads quickly on mobile devices, but that isn't designed specifically for any one device. This is a good way to do cater to mobile devices, although if your main site design is good enough it may not be necessary.
Sites that are optimized for mobile essentially have to be lighter and smaller. They should be rid of any superfluous images or design elements. There are a couple of reasons for this - 1) mobile devices often have slow or unreliable internet connections, and 2) mobile devices have very small screens. Most modern smartphones are capable of displaying large, complex sites, but navigation can be difficult.
A mobile version of a website still has the same content and is still written the same way (with XHTML / CSS), but it is usually just text or very few images, and navigation and text are large and easy to scroll through. This makes it easy to read the site on a small screen, and to move form page to page. A mobile site may resemble a print version of a webpage - all the content, but without unusual colors or design elements unless they are a part of the content (like a picture that's part of an article).
Having a site optimized for mobile devices isn't necessary, but it's a good idea, and it's especially important for sites which are more likely to have mobile visitors. You may want to use some sort of analytics software to see how many of your visitors come from mobile devices, to see if it is worth the effort to optimize for mobile. Napraui Sajt offers optimization of sites for mobile devices, and we can develop great-looking, highly-functional websites that are targeted at mobile devices.
