我们用这样的方法来加载默认的Firefox配置文件（你可以创建自定义配置文件并加载它）：

We use such method to load default firefox profile (you can create custom profile and load it):

private IWebDriver driver;  
string pathToCurrentUserProfiles = Environment.ExpandEnvironmentVariables("%APPDATA%") + @"\Mozilla\Firefox\Profiles"; // Path to profile
string[] pathsToProfiles = Directory.GetDirectories(pathToCurrentUserProfiles, "*.default", SearchOption.TopDirectoryOnly);
if (pathsToProfiles.Length != 0)
{
     FirefoxProfile profile = new FirefoxProfile(pathsToProfiles[0]);
     profile.SetPreference("browser.tabs.loadInBackground", false); // set preferences you need
     driver = new FirefoxDriver(new FirefoxBinary(), profile, serverTimeout);
}
else
{
     driver = new FirefoxDriver();
}