Looks like the hosting is on a very old server not updated for ages.
- You are using very old PHP 5.3 (more than 10 years old). All hosts should at least have an option to update to a newer PHP version. Updating to a newer PHP version MIGHT solve the panel problem.
- You are using Apache 2.0 released in 2002. Most servers use Apache 2.4, although some servers still use old Apache 2.2 from 2005. Apache 2.0 still? Unbelievable any hosting company still has this.
Perhaps most suspicious though, your server is returning
"Status Code: 302 Found" when attempting to access the
login.php page through a POST request (from login page). This is basically a clear indication that your server has some kinda FIREWALL that is blocking the POST request to this file, of course incorrectly. How are you supposed to login if they are blocking POST request to /panel/login.php? You will need to ask your host.
The file clearly exists when accessed directly in browser:
http://www.pulverfoton.cz/panel/login.php
Your host chooses to return "file not found" when the script above is POSTED to.