Which extension should I choose for my HTML files and why?
same thing.. makes no difference at all... htm was used in the days where only 3 letter extensions were common.
If you plan on putting the files on a machine supporting only 8.3 naming convention, you should limit the extension to 3 characters.
Otherwise, better choose the more descriptive .html version.
.html
- DOS has been dead for a long time. But it doesn't really make much difference in the end.
The short answer
There is none. They are exactly the same.
The long answer
Both .htm and .html are exactly the same and will work in the same way. The choice is down to personal preference, providing you’re consistent with your file naming you won’t have a problem with either.
Depending on the configuration of the web server, one of the file types will take precedence over the other. This should not be an issue since it’s unlikely that you’ll have both index.htm and index.html sitting in the same folder.
We always use the shorter .htm for our file names since file extensions are typically 3 characters long.
AND MORE ON :http://www.sightspecific.com/~mosh/WWW_FAQ/ext.html
Since nowadays, computers support widely any length as file type, the choice is now only personal. Back in the early days of Windows where only 3 letters where supported, you had to use .htm, but not anymore.
Neither!
If you're asking; "what would a website visitor rather type, htm or html" - it's much better to give them a nice descriptive URL with no extension. If they get used to going to yoursite/contact.html and you change it to yoursite/contact.php you've broken that link. If you use yoursite/contact/ then there's no problem when you switch technology.
It's the same in terms of functionality and support. (most OS recognize both, most Search Engines recognize both)
For my everyday use, I choose .htm because it's shorter to type by 25%.