If your website's root directory contains more than one index file(index.html, index.php, index.asp, etc.), Plesk will load the index file with a higher priority.  You can change the index file priority by setting the Default Document.

To set the default document:

1. Log into your Plesk Control Panel
2. Click Website & Domains
   
   
3. Locate the domain you want to modify and click SHOW MORE
   
   
4. Click Virtual Directories
   
   
5. Click Directory Properties
   
   
6. Navigate to the Documents section and click on the default document you want to use.
   
7. Click Up to move it to the top of the list.  Alternatively, you can type the file name for your default document if it is not in the list.
   
8. Click OK