...

getApplication().getRequestCycleSettings().setGatherExtendedBrowserInfo(true);

WebClientInfo w = (WebClientInfo)getWebRequestCycle().getClientInfo();
ClientProperties cp = w.getProperties();

// do something with the data
cp.getNavigatorAppName();
cp.getNavigatorAppCodeName();
cp.getNavigatorAppVersion();
cp.getBrowserVersionMajor();
cp.getBrowserVersionMinor();
...