At the risk of sounding dumb, what is the difference between naming your files .htm or .html? I don't see a difference...

.htm was used way back in the day when people used DOS to make pages and there was an 8 character limit so the shorter the better.... .html is the 'proper' way to save files, a few servers wont allow .htm pages as the index...but other than that theres no real difference between the two and either will generally work.