The list of default documents (pages which IIS will serve when only the sub directory is specified in the URL) in order of priority are: 

index.cgi, index.pl, Default.asp, index.asp, index.html, index.html.var, index.shtml, index.php, index.php3, Default.htm, index.htm, iisstart.htm, 
default.aspx,index.aspx 

The list for Linux servers is as follows 

index.cgi, index.pl, index.asp, index.html, index.html.var, index.shtml, 
index.php, index.php3, index.htm, default.htm, default.asp