How can I set a virtual server to have a index page with a shtml extension??

thanks

Assumptions: Your using Apache ;)

You need to check your srm.conf file
/etc/httpd/conf

There should be a DirectoryIndex line to allow you to specify what files should be considered index.html.
These files will be loaded when you call
http://www.mydomain.com/
and do not specify a file name.

Here's and example:
DirectoryIndex index.html index.htm index.shtml home.html home.htm default.html ..... and so on

the name can be anything....

I believe index directives are listed in order of preference....

This means if you have an index.html file AND an index.shtml file the index.shtml file will be ignored.