see more in the GitHub Flavored Markdown Spec
1 spaces
2 spaces
3 spaces
4 spaces (wrong) - rendering as code block
More than three characters may be used spec source :
Spaces are allowed between the characters spec source :
Spaces are allowed between the characters spec source :
Spaces are allowed between the characters spec source :
Spaces are allowed at the end spec source :
no other characters may occur in the line: spec source :
_ _ _ _ a
a------
---a---