When you define a default page for your Web site in the database properties, that page can only be a static page (4D will not parse it when it sends it).

To work around that limitation, you can put the following statement in the On Web Connection database method:
C_Text($1)
If ($1="/")
SEND HTML FILE (MyFile.shtm)
end if

When a request comes in for the default page (null string in the URL), the page referred to in the SEND HTML statement is then parsed and sent.