.htm or .html extension - which one is correct and what is different?

Question

When I save a file with an .htm or .html extension, which one is correct and what is different?

Answer 1

Neither is wrong, it's a matter of preference. Traditionally, MS software uses htm by default, and *nix prefers html.

As oded pointed out below, the .htm tradition was carried over from win 3.xx, where file extensions were limited to three characters.