First, read the English article below.

You can use Twitter Counter to keep tabs on who unfollows you, as well as dozens of other metrics for your Twitter account.   The service is not free, but you can sign up for a 30-day free trial. You have to provide a credit card number or PayPal information to start the trial. After the end of the trial, your account will be billed for the subscription price (unless you cancel first).  The button is at the top right corner of the screen and displays a blue Twitter logo. If you see a place to enter a username and password instead, enter your Twitter account information to log in. You should see the Authorize App button now. If you don’t want to follow Twitter Counter on Twitter, uncheck the box next to “Follow @theCounter.” If you don’t want to automatically follow Twitter users featured by Twitter Counter, remove the check next to “Discover interesting people.” Twitter Counter will email the specified address with tips on how to use the site. It’s a grayed-out link on the left sidebar. Note that you won’t have any unfollowers listed yet, as Twitter Counter just started monitoring your account. They differ in amount of accounts the site can monitor, maximum date range, support options, and available report types. The button appears at the bottom of each plan option. Be sure to click the one beneath the plan you want to try out. After the trial is over, you won’t be able to use Twitter Counter to see who unfollowed you unless you pay for a subscription. ” Choose between “Credit Card” and “PayPal.”  ” This option appears for both credit cards and PayPal. Once your card is processed, you should see the dashboard. This is where you’ll find out who unfollowed you in the future. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Mở trình duyệt web. Truy cập http://twittercounter.com/. Nhấp vào Sign In. Nhấp vào Authorize App. Nhập địa chỉ email của bạn. Nhấp vào Let’s get started (Bắt đầu). Nhấp vào liên kết “unfollowers” màu xám nằm trong thanh bên trái. Xem qua những gói có sẵn. Nhấp vào Start Free Trial (Bắt đầu dùng thử miễn phí). Nhấp vào “Next Step” (Bước tiếp theo). Chọn phương thức thanh toán. Nhập thông tin thanh toán hoặc tài khoản của bạn. Nhấp vào “Process Card” (Xử lý thẻ). Nhấp vào liên kết “unfollowers”.