Sharepoint - HTTP 503 "Service unavailable" error messages when attempting to open SharePoint Central Administration

The problem was because of change of password . All application were getting stopped so followed below steps

1. In Administrative tools, click Internet Information Services Manager.

2. For the identity of the site or Central Administration application pool is a domain user account that has an expired password, do the following:

   a. Right-click the application pool name and select Advanced Settings.

   b. Select Identity and click the … button to open the Application Pool Identity dialog box.

   c. Click Set.

   d. Type the username and password.

3. Run IISRESET. To do this, open an Administrator command prompt and type iisreset at the command.

4. In SharePoint Central Administration, in Security, select Configure managed accounts.

5. Click Edit to update the information of the managed account that has the expired password.

6. Select Change password now.

7. Click Use existing password.

8. Type the password, and then click OK.

Go to Start -> Administrative Tools -> IIS Manager -> open Application Pools -> start SharePoint Central Administration v4 app pool. Cause sometimes pool may be not started after deployment or IIS reset