There are several levels of friendliness. You can start with the basic “Does this site make it good enough to be usable in a mobile browser?” It really should not be a problem for anything new using modern web standards, but older sites may have problems. Corallary to this - "my site is a bandwidth that takes forever to display more than 3 g, because each page is 14 MB of animated GIF files and HTML spaghetti?" Or "does my site make mobile devices melt due to aggressive scenarios?" Fortunately, this set is pretty easy to handle - modern websites tend to do this pretty well by default.
Second level: "does this site do something crazy in terms of touch." The big thing that can fix you here is menu-based guidance - there is n’t any on the touch interface. Another common problem is the use of small links or buttons that cannot be hit even without approaching crazy levels. The solution here is testing - some problems are obvious to everyone, but you will not see some things until you interact without a mouse.
The last level uses a touch interface for fun and profit. If you do it this far, you do better than many web publishers that day and age. It uses user-friendly user interface tools, such as jQuery mobile, to handle broadcast events and other touch functions to make the work more similar to the Touch user interface. A simple example would be to use an image carousel rather than waiting for buttons.