shtml vs. asp for SSI

I've got a template set up using the include statement to put a standard header and footer on each of my pages. It seems to work fine using either .asp or .shtml as the prefix. Does anyone care to comment on how to decide between the two? The only thing I can think of is that using .asp might give us more flexibility later. Are there any server work effort issues here?

Thanks.

I do believe this is a matter of preference. Your server is set up to parse both shtml and asp extensions. If you want people to know that you are using asp then use that extension. If you want to hide it then use the other.