ImageBrowserURL
Defines the URL to load when clicking the "Browse Server" button in the image dialog. It can point to the default File Browser"
FCKConfig.ImageBrowserURL = FCKConfig.BasePath + 'filemanager/browser/default/browser.html?Connector=../../connectors/' + _FileBrowserLanguage + '/connector.' + _FileBrowserExtension ;
or for any custom implementation:
FCKConfig.ImageBrowserURL = '/myfilebrowserpath/browser.php' ;