shtml stands for 'server-parsed html'.
the shtml extension is needed to use server-side includes in your web pages.
e.g. you have a cgi script that counts the hits you get on your page, and prints the number of hits, and you want to have that number in your page somewhere. then you have to rename the bla.html file to bla.shtml so the webserver knows it has to be parsed. then the server will execute the code for your counter, and print the output from that script to your (s)html page.
hmm. i'm not that good in explaining stuff, but this should help you a bit http://www.devshed.com/Talk/Forums/smile.gif