A lot of you have installed Mobile Plugins to make your site mobile friendly – plugins like WP Touch or WP Mobile. These plugins will react to the user’s device to present a mobile theme but they are NOT responsive.
Mobile themes and responsive themes are different!
Mobile themes detect the user’s device/cell phone and display a theme.
Responsive themes detect the width of the screen and display the site within those parameters.
The difference is HUGE. When company XYZ puts out a new size of mobile device, your responsive site is fine – the mobile site, not so much. Responsive design is defined as working on a mobile device (not just a cell phone).
To check if your site is mobile friendly, just “restore down” the browser you’re reading this in. Then, drag the width left and right to see it shrink.