Could someone please tell me what the difference is in using the extention .html as aposed to just .htm?

Well...there is no real difference. The browser will read it correctly either way. Most servers have .html as the default, but all servers (that I know of) will read both.

Woohooo is right, There is no real difference.

I do suggest useing one or the other and not mixing though, just makes things look nice

whats the point then?...spose it would seem tidy to have em all the same throughout your website, but then again whos going to care!

..Just read the second line of your post ACJ..

nothing that I know of. (^_^)

I thought .htm was the file type for WYSISWG editors and that .html was hand coded

Not necessarily. However, WYSIWYG editors to tend to use *.htm. Dunno why. I believe our good friend FrontPage began that trend.

Time was all you had was three characters for an extension. With most, if not all, OSes letting you have extensions greater than three characters there shouldn't be any more compatibility issues. WYSIWYG programs probably use .htm by default because at one time it avoided having a site with mixed .htm and .html files. Once that's programmed in there's no good reason to change it, so it just stayed that way.

.html is the original extension. UNIX-based systems have no problem with different length file extensions. The .htm extension comes from the old Microsoft DOS 8.3 naming format where files were limited to 8 characters in their names, dot and then a 3 letter file extension. This is no longer a limitation in Windows 95 and higher.
Both are widely supported now so it really comes down to personal preference but be consistent.
The server could be configured to recognise any file extension as one associated with a particular technology such as php, asp or markup.