The default document extensions in order of rank are:
Please note that the above are listed in rank order. Therefore, if you have both an index.htm page and a default.htm page in a directory, then the index.htm will be shown as default because it is ranked higher. Similarly, if you have an index.asp page and a default.aspx page, then the index.asp page will be shown as default, because it is ranked higher.
We recommend only having one of the above default documents in your directories.