I'm not sure why you have it forwarding to your router first, if I read that correctly. I would let Plesk handle the DNS management.
On the index.html being the default page, are you saying if you go to
www.domain.com/ nothing show up but an error page? But if you go to
www.domain.com/index.html the page does show up?
In that case it sounds like a problem with the httpd.conf file.
Two ways to fix that. Assuming you're on a Linux-Plesk sysetm, and if you have root ssh ability log in to the server and edit this file. Like:
nano -w /etc/httpd/conf/httpd.conf Look for the DirectoryIndex line and make sure it has index.html listed there. Then restart apache.
If you don't have root ssh ability you should be able to do the same thing via an .htaccess file for the domain. Create an .htaccess file and put it at the root level for the domain containing a line that says
DirectoryIndex index.html
Another possibility, if you get some other default page, is that the domain may have another default index file that was created when the domain was. Check to make sure there's not another index.htm or index.php or something like that when you FTP in to the domain.
FWIW, the How To section of the forum isn't for asking questions on how to do something. It's supposed to be for people to post tutorials/instructions on how to do something. Something to remember for the future so that the forum mods don't have to work so hard to move posts around.
