Before you make any changes to your template, it's good practice to make backups first. Rest assured, you'll have a good copy to revert to if things go stylishly wrong. Template backups are easy!
Design TabAfter you log in to Blogger, choose the Blog you want to backup and click the Design Tab and then click on Edit HTML.
To save a backupClick on the Download Full Template link and save the XML file to your computer.
That's it -- that's all you need to do to save a backup of your template.
To restore a backupFollow the same steps above: click on the Design Tab and then click on Edit HTML. Then, select the XML backup file from your computer and click on Upload.
That's it -- you're all done! :)