What is mobile usability?
Mobile usability problems are issues that can affect the page when visited on a mobile device, including small font sizes (which are hard to read on a small screen) and use of Flash (which isn't supported by most mobile devices).
Why is mobile website important?
A mobile-friendly website gives your website visitors a visually appealing, enjoyable encounter with your company. Site navigation is simple and intuitive. Sharing content is natural and easy. Best of all, the site loads quickly and the text is easy to read and fits on the small screen.