Note that this is for Blogger only. Do research if your blog is on another platform.
Step 1. SAVE YOUR TEMPLATE: First, go to your blog's dashboard just like you were going to edit a post.
See way over in the upper right corner where it says "Backup/Restore"? Click there.
Choose "Download full template." A file full of code will be downloaded. Save the file and I suggest, rename it to include the current date.
Close the Backup/Restore window. Step one is done.
Step 2. SAVE YOUR CONTENT: Still on your blog's dashboard, click "Settings" in the left hand column, then "Other." See under "Import & back up" the choice to "Back up Content." Click there and another file full of code will be downloaded. This one will take a little longer than the template, but not long. Save the file and again, rename it to include the current date.
That's it! Seriously, it'll take you ten minutes or so. And give you a whole lot more peace of mind.