HTTP Error 503. The service is unavailable in IIS [Solved]

HTTP Error 503. The service is unavailable in IIS  is caused if application pool is paused or disabled as shown in the picture below:

Steps to solve HTTP Error 503. The service is unavailable are as follows:

Step 1: Open IIS and look for the  application pool of the selected website. here in this example the website name is test.

Step 2: Select the Application Pool as shown in the diagram below:

Step 3:Write click on the website name in the Application Pool and then click  on Start as shown in the picture below:

Browse the website and the error would be resolved.