Choosing between htm and html extension- as follows:
First determine what is the directory path to this page.
Next, basic ASP If script will determine the return index..
Here is script to reach the return page.
<%
Dim strDir
strDir =Server.MapPath(".")
If strDir="D:\InetPub\vhosts\crystalcomputerconcepts.com\httpdocs\ASPtestSite" Then
Response.Write("<p>Return to <a href='index.html'>Table of Contents</a></p>")
Else
Response.Write("<p>Return to <a href='index.htm'>Table of Contents</a></p>")
End If
%>
Return to Table of Contents