For webservers, the default index page (what loads when you load your website's root) is index.html. Renaming default.html to index.html will fix that.
I'm having no issues loading it right now. We /are/ performing kernel upgrades... but absolut was already restarted. The server is up and functioning.
root@absolut [~]# uptime
22:09:27 up 17 min, 2 users, load average: 4.46, 5.65, 4.16
Your server is currently rebooting for a kernel upgrade, so I can't quite see the issue.. but I bet your default page is cached. Try clearing your internet browser cache and also your DNS resolver cache (You can see more about this on our wiki: http://x10hosting.com/wiki )
The 404 error is because of your permalinks/SEO friendly urls.
As for the other issue... I'm not sure that is an issue with the server, but rather with the theme or script.
Moving to scripts/programming
Planetminecraft.com doesn't use a "frame" to have their forum. They created a custom theme that matches the rest of their website. This isn't a cPanel functionality, it's a coding functionality.