Don't run as root
From MEPIS Documentation Wiki
Some reasons for not running as root (logging in to KDE as root):
For example when you download a program from the internet: If you run it as root it has access to all the resources of the OS -- so if it's either malicious or poor programmed it can take over your computer, destroy data, etc. If you run it only as user then it can damage only the data the local user can access.
Also, if the browser, ssh, ftp, or any other network program that you use has a security hole and you run it as root if someone breaks through, they will have full control of your computer, while if you run as a normal user they will have limited access which makes it difficult to change system wide configuration files, run restricted programs, or modify the logs to hide their intrusion.