Content Query Webpart is missing newly created itemstyle

Steps to re-produce :
1. Add a new ItemStyle for the Content Query Webpart into the ItemStyle.xsl file.
2. Navigate to the ContentQuery Webpart and Apply the newly added ItemStyle.
3. You should now be able to see the new ItemStyle for the ContentQuery Webpart.
4. Login with some other User Credentials and check the ContentQuery Webpart again.

Error : ItemStyle is missing ????

Reason:
This is because ItemStyle.xsl has been checked out to the Original User who made changes by adding the new ItemStyle and forget to checkin the file.

Resolution:
Simply re-login with the user credentials you have used to make changes to ItemStyle and Check-in the ItemStyle.xsl file.

Steps:
1. Login with the user credentials you have used to make changes to ItemStyle
2. Navigate to top-level site collection
3. Click on View All Items
4. Open the Style Library
5. Check-in the ItemStyle.xsl file