Sometimes Blogspot won't do exactly what you want it to, so you need to have a few tricks up your sleeve to get it to do your bidding.
If you think you've added spaces between your paragraphs, but when you publish your post, your paragraphs are all right on top of each other, here's what you do:
- In Edit Posts mode, move your cursor to the beginning of the paragraph you'd like spaced down a line.
- Hold down the Shift key and press Enter until your paragraph is spaced the way you like it.
- Publish Post.
- View Blog, and make sure the space is there. If not, repeat this process, and it should look just the way you want it.