the onlineStatus component renders an element that will allow css to change depending on what the online state of the browser is. It also has the abilit to trigger javascript functions whenever the device or browser goess offline or online

Simply place the online status component on the page and define the class and/or js function then place the device or browser offline to test

    <mobi:onlineStatus
        onlineStyleClass="onlineStyle"
        offlineStyleClass="offlineStyle"
        onOnline="online();"
        onOffline="offline();"/>

To test simply turn your device to airport mode or desktop browsers to work offline (see offline browsing for your desktop browser).