Back up content because it's valuable to us, we spend time writing and creating it, and it would be awful to lose it. Plus, if you blog on Blogger, then you don't own your blog site. This means that your blog could be removed without warning (not likely, but not impossible), or inadvertently deleted. Both of these would be catastrophic if you have no backups of work you've created in the blog.
To avoid this, backup your content, perhaps once a week, and that way your words and images will be safe. At present Blogger still hosts my photos but this is something I'm planning on changing soon. I do however hold onto copies of all the images I use on my blog. But I often write my posts in Blogger, from scratch, and don't have any separate copy of them unless I back up my blog. If anything does happen to my blog, I can start again, using the backups to rebuild the blog. That's the theory anyway. It's an insurance policy really, and chances are I, and you, will never have to use it.
Back up the template in case you inadvertently make alternations that you can't undo, and that change the look of your blog irreparably. Once it's done, it's done and such mistakes can happen even when you're trying to do something else. If you back up the template before you make any changes, even very simple ones, then you never have to worry about having to start from the beginning again.
I have made this mistake in the past, playing around with my blog and then discovering I couldn't change back what I'd done - this doesn't always involve opening the template up and editing it. Sometimes a simple widget addition can alter things in a way you don't want, so having a backed up template means you can retrace your steps with ease and not hours of angst instead...
Here's how to go about backing up your blog.
To backup the content
3. Download your blog to your computer.
4. Save the file - it will save wherever your downloaded files normally save. I move my saved file to the folder I keep everything for my blog in, so I know where it is, and I rename it something I'll recognise easily. It's also worth putting it on a memory stick as well, as extra backup. Well, you never know...
To backup the template
b. Download full template - again, it will save to your downloaded files area. And again, it's worth moving it somewhere you know you'll be able to find it easily, renaming it, and backing it up yet again as extra insurance.
I think once you get into the habit of doing this, it doesn't take too much time and effort. We all know we should backup and we never do it enough. I know I have some photos on my computer that are only on my computer at the moment...and that makes me nervous. I must back up!
Hope this has been some help.
Further informationhttps://support.google.com/blogger/answer/97416 - Basic Google/Blogger instructions